Radio-opaque compounds, compositions containing same and methods of their synthesis and use

ABSTRACT

Radio-opaque biodegradable compositions are formed by modifying terminal groups of synthetic and natural biodegradable polymers such as polylactones with iodinated moieties. The biodegradable property of the compositions renders them suitable for use in medical field such as drug delivery, imaging. Compounds disclosed in this invention exist as neat liquid. Certain compositions disclosed in this invention form hydrophobic iodine rich domains when dissolved in water, such domains provide better contrasting properties as well as ability to dissolve hydrophobic bioactive drugs. Certain iodinated moieties disclosed in the invention are capable of cross linking natural proteins in situ in presence of suitable catalysts and co-catalysts.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/840,376, filed Jul. 21, 2010, now U.S. Pat. No. 8,273,327, which is acontinuation of U.S. patent application Ser. No. 10/914,701, filed Aug.9, 2004, now U.S. Pat. No. 7,790,141, which claims priority of U.S.Provisional Application No. 60/494,340 filed Aug. 11, 2003, each ofwhich are hereby incorporated herein by reference.

BACKGROUND

This present invention relates to biodegradable radio-opaque compoundsthat can be used as contrast agents in medical imaging, surgical markersand for localized drug delivery. The invention also relates toradio-opaque compounds, compositions containing such compounds andmethods of their synthesis and use.

DEFINITIONS

All scientific and technical terms used herein have the same meaning asis commonly understood by one skilled in the synthetic polymerchemistry, polyethylene glycol modification chemistry, controlled drugdelivery and synthetic biodegradable chemistry art, and to which thisinvention belongs; unless it is defined specifically for this invention.

“Oligomers” are defined as low molecular weight polymeric compounds. Inthis invention, oligomers may be defined as polymeric compounds withmolecular weight between 40-2000 Daltons.

“Cross-linked material” is meant to denote the conversion of a solublematerial to an insoluble state. The crosslinked material may still be ina highly hydrated state.

“In situ” is meant to denote at a local site, especially within or incontact with living organisms, tissue, organs, or the body.

“Bioactive” as used herein, refers to one or all of the activities of acompound that show pharmacological or biological activity in human oranimal body. Such biological activity is preferred to have therapeuticeffect. The bioactive compounds that can be used include, but notlimited to: antiviral agents; antiinfectives such as antibiotics;antipruritics; antipsychotics; cholesterol or lipid reducing agents,cell cycle inhibitors, anticancer agents, antiparkinsonism drugs,HMG-CoA inhibitors, antirestenosis agents, antiinflammatory agents;antiasthmatic agents; antihelmintics; immunosuppressives; musclerelaxants; antidiuretic agents; vasodilators; nitric oxide, nitric oxidereleasing compounds, beta-blockers; hormones; antidepressants;decongestants; calcium channel blockers; growth factors such as bonegrowth factors, wound healing agents, analgesics and analgesiccombinations; local anesthetics agents, antihistamines; sedatives;angiogenesis promoting agents; angiogenesis inhibiting agents;tranquilizers and the like. Cellular elements which be used fortherapeutic use such as mammalian cells including stem cells, cellularcomponents or fragments, enzymes, DNA, RNA, genes may also be includedas bioactive components.

“Biodegradable” is meant to denote a material that will degrade in abiological environment by either a biologically assisted mechanism, suchas an enzyme catalyzed reaction or by a chemical mechanism which canoccur in a biological medium, such as hydrolysis.

“Biostable” is meant to denote a high chemical stability of a compoundin an aqueous environment, which is similar to the environment, found inthe human body such as phosphate buffered saline (pH 7.2).

“Injectable composition” means any polymeric or non-polymericcomposition that can be injected as a liquid and converted into solidinside a human body using minimally invasive surgical devices.

Polyethylene glycol (PEG) or polyethylene oxide (PEO) refers to the samepolymer which is made by polymerization of ethylene oxide.

Polymeric nomenclature used in this patent application such as poly(lactic acid) or polylactic acid or polylacticacid refer to the samepolymer, unless otherwise stated clearly. This is also true for allothers polymers referred in this patent application.

The radio-opaque nature of many compounds allows them to be tracedwithin a human or an animal body and therefore such compounds findapplication in medical diagnostics and pharmaceutical field. Some of theapplications of such radio opaque compounds include medical imagingapplications such as x-rays, angiography, urography, phlebography anddrug delivery at a localized site.

In medical imaging techniques such as X-ray imaging, attenuation of softtissue by x-ray radiation can be improved by exogenously administering aradio-opaque compound, which gets distributed in the tissue to beimaged. The infused compound preferentially absorbs x-ray radiation inthe tissue and therefore improves quality of the image. Such improvedimage results in better diagnosis of the medical condition.

It is desired that such compounds should mix with the body fluidswithout causing significant change in the local chemical environmentsuch as osmolarity, which is concentration of the solute per unit oftotal volume of solution and pH, should be economically feasible,chemically stable, highly water soluble, readily injectable with lowviscosity and a ready to inject solution, biologically inert and shouldbe removable safely and completely by the body.

The radio opaque compounds reported in the prior art generally fall intotwo categories: ionic and non-ionic. The ionic monomeric compounds usedas contrast media for intravascular use have an osmolarity seven toeight times that of normal human blood. This hyper-osmolarity is partlybelieved to be responsible for several subjective and objective adverseeffects such as pain, endothelial damage, thrombosis andthrombophlebitis, disturbance of the blood-brain barrier, bradycardia incardioangiography and increased pressure in the pulmonary circulation.On the other hand, non-ionic compounds such as Iohexyl, Iopamidol,metrizamide are formulated as less hyperosmolar solutions. However, thecurrent non-ionic radio opaque compounds are much more expensive andexhibit relatively high rate of adverse events. In a recent smallclinical study, two non-ionic media containing Iohexyl and loversol werecompared. More than 10% patients, receiving either Iohexyl or loversolreported adverse events, which were categorized from mild to moderate tosevere. These events included dizziness, pruritus, apnea, fever,purpura, blurred vision, headache, urticaria, congestion,lightheadedness, vertigo, cough, metallic taste, disorientation, andnausea. Hence, the side effects of these ionic as well as non-ioniccontrast agents cannot be overruled.

U.S. Pat. No. 5,746,998 titled “Targeted co-polymers for radiographicimaging” describes polymeric compounds such as diblock copolymerscapable of forming micelles for medical imaging. The block copolymers, acombination of two polymers, and high molecular weight are essential toform micelles. Such polymers require several multistep synthesisprocedures. In addition, water soluble biologically intert polymers suchas polyethylene oxide or poly (vinyl pyrrolidinone), with molecularweight above 20,000 g/mol are not eliminated by the body and thereforeare stored inside the body. Thus high molecular weight polymers above20,000 are considered as non-degradable permanent implants. On the otherhand, polyethylene glycol with a molecular weight below 300 is insolublein water. Water solubility is considered essential for safe removal ofthe compound. Many derivatives of polyethylene oxide such aspolyethylene glycol succinate based derivatives, glutaric acid basedderivatives and hydroxy acid based derivatives undergo substantialhydrolysis and degradation when stored in water for prolonged periods oftime. Such degradation leads to unstable formulations and may have toxiceffects on the human body.

Also, ionized polymers used for medical imaging applications canincrease the osmolarity of the injectable solution with their counterions. This may lead to several adverse effects as pain, endothelialdamage, and the like. For example, polylysine is considered as a chargedpolymer and must be ionized to bring its pH to physiological range.

In addition, polyethylene glycol (PEG) based compounds used for theseapplications are also susceptible for oxidative reaction, which can formtoxic peroxide radicals. These PEG based compounds must be combined withantioxidants to improve shelf life and prevent oxidative relatedreactions.

Along with medical imaging, some of the radio-opaque polymers that arebiodegradable have received considerable interest in the medical andpharmaceutical field, as they can perform temporary therapeutic functionand are eliminated from the body once the therapeutic function has beenaccomplished. Some of the well-known applications of biodegradablepolymers include surgical sutures, staples or other wound closuredevices, as a carrier for bioactive substances for controlled drugdelivery etc. Among the biodegradable polymers reported in the priorart, polymers prepared from hydroxy acids and/or polylactones havereceived much attention due to their degradability and toxicologicalsafety. Homopolymers and copolymers based on the l-lactic acid,dl-lactic acid and glycolic acid are among the most widely used polymersfor medical applications. These polymers can be formulated into varietyof physical forms such as fibers or filaments with acceptable mechanicalproperties, degradation profile and non-toxic degradation products.

To visualize the deployment of bioabsorbable implantable devices in thehuman or animal body, many surgical procedures are performed with theaid of fluoroscopic angiography. However, most biodegradable polymersused in current clinical practice have poor visibility when viewed usingstandard medical imaging equipment. The absorbable polymeric materialmay be visualized if they are radio-opaque and offer radiographiccontrast relative to the body. To make the absorbable polymerradio-opaque, it must be made from a material possessing radiographicdensity higher than surrounding host tissue, and have sufficientthickness to affect the transmission of radiations and produce acontrast in the image. To improve the visualization, the biodegradablepolymer must be chemically and physically modified.

U.S. Pat. No. 6,174,330 titled “Bioabsorbable marker having radio-opaqueconstituents” discloses use of bioabsorbable polymer mixed withnon-absorbable radio-opaque moieties such as heavy metal compounds mixedwith the absorbable polymer. U.S. Pat. No. 6,475,477 titled“Radio-opaque polymer biomaterials” discloses tyrosine derivedradio-opaque polymers.

However, current technologies may not be able provide radio-opaquebiodegradable polymers that are degraded and completely eliminated bythe body and also have good visibility when administered in a human oran animal body.

The above-mentioned limitation linked to biodegradable radio-opaquepolymers is also applicable to Minimal Invasive Surgery (MIS)techniques. Minimally invasive surgery (MIS) encompasses laparoscopy,thoracoscopy, arthroscopy, intraluminal endoscopy, endovasculartechniques; catheter based cardiac techniques such as balloonangioplasty, interventional radiology and the like. These proceduresallow mechanical access to the interior of the body with the leastpossible perturbation of the patient's body. Many MIS procedures involvevery small mechanical tools such as catheters or trocars that aremanipulated outside the patient's body but are capable of performingtheir function within the patient's body. Biodegradable polymers thatcan be used with MIS procedures are becoming increasingly important.These polymers are used as sutures, surgical clips, staples, sealants,tissue coatings, implants and drug delivery systems. The polymers thatare used with MIS applications are either preformed or are generatedin-situ. However, the visibility of these polymers when administered ina human or an animal body is low. In many MIS applications, it isessential to transport the material at the surgical site. Theradio-opacity helps to monitor the movement of implant from the site ofimplantation or degradation of implant. Radio-opacity also helps tolocate and retrieved the biodegradable implant if necessary. Thusradio-opacity offers many useful functionalities, which may help tooffer better medical treatments.

A need exists for radio-opaque polymers that are easily degraded in thebody and have no side effects. There is also a need of polymers thathave a good visibility under medical imaging scanners. There is furthera need for injectable biodegradable polymeric compositions that areradio-opaque and can be used to deliver bioactive drugs using MIStechniques.

SUMMARY

In the light above discussion, it is the object of the present inventionto provide oligomeric, homopolymeric, water soluble, hydrolyticallystable and non-ionic compounds and compositions useful in medicaldiagnostic and pharmaceutical field.

Another object of this invention is to provide contrast agentcompositions, which self assemble in water forming iodine rich domainsfor use in x-ray imaging and localized delivery of bioactive compounds.

Another object of this invention is to provide radio opaque compoundsthat are water soluble and exist as a neat liquid at temperature between10° C. to 45° C.

Another object of this invention is to provide contrast mediacompositions that are stored and dispensed in biocompatiblesubstantially non-aqueous medium.

Yet another objective of this invention is to provide synthesis methodsfor preparation of radio opaque compounds.

Yet another objective of this invention is to provide methods forpreparation of compositions containing radio opaque compounds.

Another object of this invention is to provide polyether based compoundswith iodinated xanthene moieties.

Another object of this invention is to provide polyether basedradio-opaque biostable compositions for controlled drug delivery.

Another object of this invention is to provide methods and compositionstissue specific contrast enhancing compositions. More specifically,human antibodies, monoclonal human antibody whose functional groups arechemically reacted with iodinated compounds like triiodobenzene orxanthene derivatives. Another object of this invention is to providemethods and compositions of iodinated compounds with activatedfunctional groups. Such activated compounds react with proteins undermild reaction conditions such as physiological conditions (PBS pH 7.2).

Another object of this invention to provide methods and compositions forradio-opaque natural polymers such as albumin, collagen, gelatin,antibodies, hyaluronic acid, chitosan and their use in medicalapplication such as controlled drug delivery applications.

Another object of this invention to provide methods and compositions forradio-opaque proteins such as albumin, collagen, gelatin, antibodieswherein the modified proteins are soluble in water.

Another object of this invention to provide methods and compositions forradio-opaque proteins such as albumin, collagen, gelatin, antibodieswherein the modified proteins are crosslinked using zero lengthcrosslinking agent.

Another object the invention is to provide methods and compositions ofbiodegradable polymers or biostable polymers, which are blended withiodinated compounds, more specifically with non-ionic or polymericiodinated compounds.

Another object of this invention is to provide a radio-opaquecomposition that is thermosensitive in nature.

Another object of this invention is to provide radio-opaquebiodegradable composition that can be formed in situ inside a human oranimal body.

Another objective of the invention is to provide a kit for used asinjectable crosslinkable radio-opaque formulation, wherein theconstituents may be premixed just prior to surgical procedure andinjected using MIS surgical technique.

Another object of this invention is to provide radio-opaque compositionthat can be gelled or solidified by physical cross-linking by change inphase.

Another object of this invention is to provide a process for treating acondition requiring the use of biodegradable medical device orpharmaceutical treatment, which comprises an injection into a body orbody cavity, and a hydrophobic, biodegradable radio-opaque polymer.

Another object of this invention is to provide a method for treating amedical condition requiring the use of biodegradable medical device orpharmaceutical treatment, which comprises; an injection into a body orbody cavity, and a hydrophobic, biodegradable polymer that is dissolvedin a biocompatible solvent along with x-ray contrast agent.

Another objective of this invention is to provide an implantable orinjectable composition comprising at least one biologically activecompound in a hydrophobic radio-opaque biodegradable polymer.

Another object of this invention is to provide a completelybiodegradable surgical biopsy marker.

Another object of this invention is to provide a surgical biodegradablebiopsy marker that is visible in two or more medical imaging techniques.

Another object of this invention is to provide a biopsy marker whereinthe biopsy marker has an outer skin made from hydrophobic biodegradablepolymer and a hollow interior wherein the hollow interior is filled withone or more medical imaging agent.

Another object of this invention is to provide radio-opaque proteincross-linker.

Another objective of this invention is to provide a biodegradable orbiostable radio-opaque coating composition for a biodegradable/biostablemedical device such as a biodegradable/biostable stent,biodegradable/biostable suture, biodegradable/biostable spinal implantsand cages, surgical markers biodegradable/biostable staple, clip.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of the invention will hereinafter be describedin conjunction with the appended drawings provided to illustrate and notto limit the invention, wherein like designations denote like elements,and in which:

FIG. 1 shows schematically the constituents of the radio-opaquebiodegradable polymeric compound;

FIG. 2 shows schematically exemplary structures that constitute thebiodegradable radio-opaque polymeric compound;

FIG. 3 describes an exemplary reaction procedure for synthesizingpolycaprolactone terminated with triiodobenzoic acid ester;

FIG. 4 describes an exemplary reaction procedure for polymerizingdl-lactide with triidophenol;

FIG. 5 illustrates an exemplary embodiment in which albumin is reactedwith iopamide in presence of EDC and n-hydroxysuccinimide (NHS) as acatalyst;

FIG. 6 illustrates an exemplary modification scheme for modification ofnatural polymer such as albumin or antibody using iodinated compound toproduce a substantially non-crosslinked water soluble modified polymer;

FIG. 7 is a schematic partial representation of radio opaque compoundwith three parts;

FIG. 8 illustrates exemplary structures that form part A of the radioopaque compound;

FIG. 9 illustrates exemplary structures that form part B of the radioopaque compound disclosed in the invention;

FIG. 10 illustrates examples of hydrolytically stable chemical bonds(part C) of the radio opaque compound disclosed in the invention;

FIG. 11 illustrates exemplary structural arrangements of the radioopaque compounds disclosed in the invention;

FIG. 12 illustrates an exemplary method for synthesis of the radioopaque compound provided by the invention;

FIG. 13 illustrates an exemplary method for synthesis of radio opaquecompound of the invention by modifying the hydroxyl terminal ends ofPEG; and

FIG. 14 illustrates self-assembly property of the radio opaque compoundsin aqueous medium.

DESCRIPTION OF PREFERRED EMBODIMENTS

Radio-Opaque Biodegradable Compounds and Compositions

Described herein are radio-opaque biodegradable polymeric compounds,which are used for medical applications. For these applications thepolymers may be combined with a variety of materials. Examples of suchmaterials include, but are not limited to, bioactive compounds, carriermediums, medical devices, and the like. The radio-opaque polymericcompounds may be detected by medical imaging scanners such as X-rayscanners, Magnetic resonance Imaging (MRI) scanners, Nuclear magneticResonance (NMR) scanners and Ultrasound scanners. This invention alsoprovides compositions and methods that provide radio-opaque proteincross-linkers.

FIG. 1 shows the constituents of the radio-opaque biodegradablepolymeric compound. The radio-opaque polymeric compound comprises abiodegradable polymer 102 and a radio-radio-opaque iodinated moiety 104.Biodegradable polymer 102 is linked to iodinated moiety 104 using abiodegradable chemical bond. In various embodiments of the invention,iodinated moiety 104 is linked to an end of biodegradable polymer 102.

FIG. 2 shows exemplary structures of the biodegradable radio-opaquepolymeric compound. The structures described in FIG. 2 have two parts,biodegradable region 102 and radio-radio-opaque iodinated moiety 104.Structures A and B represent a linear polymer with one or both ends ofbiodegradable region 102 modified with radio-radio-opaque iodinatedmoiety 104. Structure C shows, a branched or star shaped biodegradablepolymer terminated with radio-radio-opaque iodinated moiety 104. Inaddition, structure D shows a multi-branched star shaped biodegradablepolymer whose ends groups are substituted with radio-radio-opaqueiodinated moiety 104. Structure E shows a graft type biodegradablepolymer substituted with radio-opaque region 104. A graft like polymercan be synthesized by various methods known in the art. Examples ofgraft like polymers include copolymers of lactide and lysine,synthesized by methods known in the polymer chemistry art. The iodinatedmoiety and the graft shape biodegradable polymer may be linked using anamine functional side group. Structure F shows a multifunctionalbiodegradable polymer whose ends groups are partially substituted withradio-opaque iodinated moiety 104. In various embodiments of thebiodegradable radio-opaque polymeric compound, the unsubstituted sites(as shown in Structure F) are attached to a drug or bioactive compound.This partial substitution is desirable to obtain suitable polymerproperties.

In various embodiments, biodegradable region 102 includes polymers,copolymers or oligomers of: glycolide, dl-lactide, d-lactide, l-lactide,caprolactone, dioxanone and trimethylene carbonate; polyhydroxyacids,polylactic acid, polyglycolic acid, polyorthocarbonates, polyanhydrides,polylactones, polyaminoacids, and polyphosphates. The size or length ofbiodegradable region 102 is varied depending upon the applicationsdesired. In addition, radio-opaque iodinated moiety 104 is selected fromiodine-substituted compounds including triidobenzoic acid,triiodophenol, erythrosine, rose bengal, and their derivatives. Examplesof these derivatives include, 2,3,5-triiodobenzoic acid and3,4,5-triiodophenol. More particularly,3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid,3,5-Diacetamido-2,4,6-triiodobenzoic acid may be used, and preferably3,5-Diacetamido-2,4,6-triiodobenzoic acid may be used.

Preparation

The biodegradable radio-opaque polymeric compound of the invention ismade using synthetic biodegradable polymer synthesis methods.

Table 1 illustrates exemplary reactants and their concentration used formaking various biodegradable radio-opaque compositions.

TABLE 1 No. of Average No. of iodine Mol. wt. end- atoms PolymerBiodegradable of BP Iodinated groups per Iodine Code Polymer (BP)(Daltons) Moiety (IM) modified molecule (%) BP101 Polylactide 4030Erythrosin 3 12 37 BP102 Polycaprolactone 4271 Triiodobenzene 5 15 44BP103 Polycaprolactone 1963 Triiodobenzene 2 3 39 BP104 Polylactide 3366Triiodobenzene 1 3 11.3 BP104 Polylactide 9126 Triiodobenzene 1 3 4.17

The biodegradable polymers that may be used in the synthesis includepolylactide, polycaprolactone, and polyglycolides. In addition, theiodinated moieties that are chosen for synthesis include derivatives oferythrosine and triidobenzene. The radio-opaque moieties (as describedin Table 1) may be solid, liquid, semi-solid, gel or wax type. Thenumber of iodinated end groups and the concentration of iodine in theend compound may be varied based on the number of the iodinated endgroups linked to the terminals of the biodegradable polymers. Forexample, Polycaprolactone (BP102) has 5 end groups modified withTriidobenzene to achieve an iodine concentration of 44% by weight. Inaddition, the biodegradation of the compound will depend upon the typeof biodegradable polymer used. For example, polycaprolactone generallydegrade in 2-5 years, polylactide generally degrade in 6-24 months andpolyglycolide generally degrade in six months. The copolymers of theseand other lactones may have degradation time from one month to 5 years.

The iodinated end-capped polymers produced in accordance with theinvention can attain desirable physical and chemical properties. Thesecan be obtained by choosing structural features such as the nature ofthe end group, (hydrophobic or hydrophilic), the chain length andchemical structure of the end-group. The biodegradable polymeric segmentcan also have structural variables such as molecular weight and/ormolecular weight distribution, the chemical nature, the repeating unitof polymer or copolymer, and the nature of end group.

FIG. 3 describes an exemplary reaction procedure for synthesizingpolycaprolactone terminated with triiodobenzoic acid ester. The reactionbegins with polymerization of caprolactone (A). The reaction isinitiated by diethylene glycol (B) in the presence of stannous octoateat a temperature of 180° C. The reaction produces polycaprolactone diol(C), which has a molecular weight of 2000 Daltons and terminated withtwo hydroxyl groups. The polycaprolactone diol (C) produced is thenesterified with Triidobenzoic acid (D) in the presence of DCC as acatalyst. The resultant polymer is polycaprolactone terminated with twotriiodobenzoic acid esters. Other variations of this synthesis arepossible, such as copolymerization with glycolide or caprolactone toobtain a copolymer. This copolymer is then used in the subsequentreaction where terminal hydroxyl groups are esterified withtriiodobenzoyl chloride. In another embodiment, a 5-arm polycaprolactonepolymer is synthesized by ring opening polymerization of caprolactone.The reaction is initiated by xylitol. The 5 hydroxy groups on xylitolinitiate polymerization, producing a star polymer with hydroxy endgroups. The hydroxy end-groups are subsequently reacted withtriiodobenzoic acid to produce ester of triiodobenzoic acid.

FIG. 4 describes an exemplary reaction procedure for polymerizingdl-lactide with triidophenol or triiodobenzyl alcohol. In the reaction,the dl-lactide (A) ring is opened and polymerization is initiated bytriidophenol (B). The reaction is initiated in the presence of stannousoctoate at a temperature of 180° C. In order to obtain a desiredmolecular weight of lactide or to control the degree of polymerization,a specific ratio of lactide to triidophenol is chosen.

In another embodiment, trimethylol propane-triol is used to initiate thepolymerization of lactide and caprolactone. The low molecular liquidpolymer thus obtained was used in subsequent esterification reactionwith Erythrosine. In another embodiment of the invention, graft typepolymers are made by modifying lysine residues of gelatin or collagenchains.

In another embodiment, polyhydroxy iodinated compounds such asmetrizamide, iopamidol, iopentol, iopromide, and ioversol are used toinitiate the polymerization of lactones such as lactide and glycolide.The resultant polymer has triiodo group at the center, which providesradio-opaque properties. In another embodiment, triiodobenzyl alcohol ortriiodophenol is used to initiate polymerization of cyclic lactone.Briefly, hydroxy group on the triiodobenzyl alcohol or triiodophenol isused to initiate polymerization of cyclic lactone monomers such asglycolide and caprolactone. The method does not require additionalreactions to link iodinated moieties to the polymer. Some biodegradablepolymers such as polylactic acid may also be synthesized bypolycondensation of lactic acid. The terminal groups of such polymersmay be modified with iodine containing compounds.

Radio-Opaque Protein Modifying Agents

This invention also describes a radio-opaque protein modifying agentsand radio-opaque protein cross-linkers. These cross-linkers uponmodification and/or cross-linking show improved visibility of themodified/cross-linked composition when viewed using medical imagingequipments.

Radio-opaque protein modifying agents and cross-linkers described inthis invention have three parts including: at least one functional group(F) capable of reacting with protein preferably under mild conditions,and at least one radio-opaque chromophore (M) capable of stronglyscattering/absorbing x-ray radiation. The two parts are linked through athird part (X).

The parts of the radio-opaque protein modifying agents and cross-linkersare represented by the following structural formula:(F)_(n)—X-MWhere;n≧1

-   -   F is a functional group reactive with collagen or protein under        mild reaction conditions and preferably capable of reacting with        free primary amine groups in the protein;    -   M is a chromophore that can absorb radiations. The preferred        chromophores that are used for absorbing X-rays include, but not        limited to: phenyl ring compounds such as 2,3,5-triiodobenzoic        acid, 3,4,5-triiodophenol, erythrosine, rose bengal,        3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid,        3,5-Diacetamido-2,4,6-triiodobenzoic acid, heavy metal ion        complexes, and the like.    -   X is an organic molecule/radical covalently linking F and X. X        comprises Carbon-Carbon, Carbon-Hydrogen, Carbon-Nitrogen,        Carbon-Oxygen, Carbon-Sulfur, Nitrogen-Hydrogen and        Oxygen-Hydrogen covalent bonds. X may be polymeric or        non-polymeric in nature.

In embodiments that do not require cross-linking, only one functionalgroup (F) per molecule is chosen. This is done to avoid cross-linking ofproteins. On the other hand, if cross-linking is desired, 2 or morefunctional groups are used.

The mild reactions conditions, under which the functional group (F) canreact with proteins and form a chemical bond, include physiologicalconditions (PBS buffer, pH 7.2).

Functional groups that are reactive with collagen molecule and suitablefor use may include, but not limited to, are: anhydride, isocyanate,n-hydroxysuccinimide, n-hydroxysulfosuccinimide, epoxy, aldehyde, andother collagen reactive functionalities known in the art.

Radio-opaque cross-linker/modifying agents according to the inventionsinclude, but not limited to: activated monofunctional triiodobenzenederivatives such as n-hydroxysuccinimide esters,n-hydroxysulfosuccinimide esters of triiodobenzoic acid,3,5-Diacetamido-2,4,6-triiodobenzoic acid or Diatrizoic acid anderythrosine.

Preparation

In an exemplary embodiment, the hydroxyl groups of commerciallyavailable X-ray contrast agent are converted into carboxylic acid groupby reacting with succinic anhydride. The acid groups are then activatedwith n-hydroxysuccinimide ester or n-hydroxysulfosuccinimide to from across-linker. The n-hydroxysulfosuccinimide ester is preferred in manysituations because it provides improved water solubility presumably dueto sulfonate group on the n-hydroxysuccinimide ring. The activated acidgroups then reacts with protein in aqueous medium under mild conditions.

In another embodiment, iohexyl derivative are used to generate proteinmodifying agent/cross-linkers. Many hydroxy activated chemistries knownin the polyethylene glycol modification chemistry are used to modify theIohexyl hydroxy groups; these include but not limited to: sulfonylchloride activation chemistry, carbodiimide activation chemistry and thelike. The three iodine atoms in activated iohexyl derivative serve asX-ray absorbing chromophore. In addition, many iodinated compoundshaving multiple hydroxy groups can be used. These include but notlimited to: metrizamide, iopamidol, iopentol, iopromide, iodixanol andioversol.

After chemically bonding of Iohexyl to the protein, the modified proteinshows better X-ray contrasting ability when compared with unmodifiedprotein. The X-ray contrasting ability will depend on the amount oforganically bound iodine incorporated in the modified protein. Thepreferred amount of iodine incorporated in the protein range from 30mg/g of protein to 400 mg/g of protein. The most preferred amount ofiodine that is incorporated is in the range of 50 to 200 mg/g ofprotein.

In some medical applications such as tissue specific diagnostic imagingapplication, a radio-opaque protein that is water soluble is highlydesirable. This invention provides methods and protein based watersoluble radio-opaque compositions. In one exemplary embodiment,modification of albumin is done by n-hydroxysuccinimide ester benzoicacid or diatrizoic acid. The monofunctional modification reactionprovides iodine group incorporation without chemical cross-linking (FIG.6). The two amide group in diatrizoic acid help to enhance watersolubility of modified protein. Therefore, modification of protein withdiatrizoic acid is even more preferred. It is preferred to incorporateat least 5 to 40 percent organically bound iodine in the modifiedprotein. 10 to 20 percent organically bound iodine incorporation is evenmore preferred. The water soluble iodinated proteins especiallyantibodies could be used in diagnostics applications. The water solubleradio-opaque protein can also be used for drug delivery and contrastmedium applications.

In another approach, a radio-opaque polymerizable monomer ormacromonomer may be used in polymerization and cross-linking of protein.For example, a polymerizable radio-opaque monomer may be obtained byesterification of triiodobenzoic acid and 2-hydroxyethyl methacrylate.The radio-opaque ester may be copolymerized and cross-linked withunsaturated group modified protein.

In one embodiment, the cross-linked radio-opaque protein is lyophilized.The lyophilization creates porosity in the protein hydrogel. The airentrapped in the porous structure is useful in creating a better imagewhen viewed using ultrasonic imaging technique. The air in the poroushydrogel may be replaced by other biocompatible gas. The term“biocompatible gas” refers to any compound which is a gas or capable offorming a gas at physiological conditions present in the human or animalbody (for example at 37° C., pH 7.2). The gas or their mixtures in anyall proportions may be selected from the group comprising: oxygen,carbon dioxide, argon, nitrogen or fluorinated hydrocarbons. Among thefluorinated hydrocarbons, perfluoropropane or perfluorbutane arepreferred. Octafluoropropane and dodecafluorobutane are most preferred.The use of carbon dioxide, oxygen and octafluoropropane or theirmixtures are most preferred. The porosity along with its entrapped gasprovides better contrast when viewed using ultrasonic medical imagingequipment, and the iodine incorporation provides visibility in X-rayimaging equipment. Therefore this material is visible in two differentimaging techniques. Many hydrated materials usually have good visibilityin magnetic resonance imaging technique. Thus a radio-opaque hydrogelwith porosity with its entrapped air or gas might be useful in all threemajor medical imaging technologies. Such materials may have wideapplications in MIS surgery. The gas may be filled inside the porouspolymer by packaging under gaseous atmosphere. For example, the porousradio-opaque composition may be packaged under octafluoropropane orcarbon dioxide and the package may be opened just prior to implantation.

In an embodiment of the invention, a cross-linkable hydrophobicbiodegradable polymer such as made by free radical polymerization ofacrylate end-capped polyhydroxy acid polymer and is used as a matrix fordrug delivery. This polymer is made radio-opaque by adding aradio-opaque compound such as Metrizamide, iopamidol, iopentol,iopromide, and Ioversol prior to free radical cross-linking. Theradio-opaque compound added is physically entrapped in the polyhydroxypolymer and makes the cross-linked polymer radio-opaque.

The radio-opaque crosslinked hydrogel compositions may potentially beused to obtain synthetic radio-opaque hydrogels. A thiol or mercaptogroup reaction with organic compounds containing unsaturated groupscould also be used to obtain radio-opaque hydrogels. For example, aradio-opaque crosslinker/monomer containing two or more unsaturatedgroups can be reacted with synthetic polymer such as polyethylene glycolderivative containing two or more amine or thiol functional groups toobtain a crosslinked hydrogel. In another variation of this approach,unsaturated polyethylene glycol based monomers such as polyethyleneglycol diacrylate or methacrylate may be reacted with iodinatedcompounds two or more thiol groups to obtain radio-opaque hydrogels.

Natural Polymer Based Compositions

The present invention also provides natural polymer based compositionsand methods useful for making radio-opaque biodegradable implants. Thecompositions described in this invention may be formed in-situ during asurgical procedure or may be formed outside in a manufacturing orlaboratory environment.

In one embodiment of the invention, a radio-opaque iodinated compoundand a catalyst that promotes a chemical bond between a natural polymerand iodinated compound is injected in-situ to form a cross-linkednatural polymer based radio-opaque hydrogel. The radio-opacity is due toiodine compound that is chemically bonded to the cross-linked naturalpolymer network.

In various embodiments of the invention, reaction between a naturalpolymer and an iodinated compound results in a biodegradable naturalpolymer based hydrogel. Examples of natural polymer include, but notlimited to: natural peptides or polypeptides, albumin, collagen,gelatin, elastin, keratin, hyaluronic acid, sodium hyaluronate,chitosan, dextran, or their derivatives and analogs and the like. Thepreferred natural polymers are albumin, collagen, gelatin, hyaluronicacid or chitosan. The natural polymer may also be obtained fromrecombinant technology or source generally known in the biotechnologyart. For example, recombinant albumin, collagen, gelatin hyaluronic acidmay be obtained form commercial sources. Hyaluronic acid made byrecombinant technology can be purchased from Genzyme Inc., Cambridge,Mass., USA. A preferred natural polymer is albumin obtained from naturalor recombinant source at a concentration at 10-50% (w/w), morepreferably between 20 to 45% (w/w) of the uncross-linked composition.

The preferred iodinated compound is water-soluble, is biocompatible, isaromatic with 3 or more iodine atoms per molecule and has functionalgroups capable reacting with natural polymers. Examples of preferrediodine compounds include, but not limited to: iohexyl, metrizamide,iopamidol, 3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid, iopentol,iopromide, triiodobenzoic acid, erythrosine and ioversol.

In various embodiments of the invention, a catalyst is used in reactionsbetween a natural polymer and an iodinated compound. A catalyst is acompound capable of assisting in formation of a chemical bond betweenthe natural polymer or protein and iodinated compound. The catalyst maybe an organic or inorganic compound or an enzyme and is preferably watersoluble. The preferred catalyst is a synthetic organic compound thatpromotes an ester, amide or urethane bond formation between protein andiodinated compounds. Catalyst that promotes a hydrolyzable bondformation, such as ester, lactone, lactam, disulfide, thioester bondformation, is even more preferred. A catalyst that does not getchemically bonded to the cross-linked/modified natural polymer is evenmore preferred. This is generally known as “zero length cross-linking”in the protein modification chemistry art. The preferred catalyst ofthis invention is a class of compounds generally known as carbodiimides.Carbodiimides have following general structure:

Carbodiimides generally promote reaction between carboxylic acid oramine and hydroxyl groups to form ester or amide bond respectively.Water soluble carbodiimides are most preferred. Water solublecarbodiimide such as 1-ethyl-3-(3-dimethylaminopropyl carbodiimide)hydrochloride (EDC) is most preferred. Other carbodiimides that can beused include but not limited to:1-(3-dimethylaminopropyl)-3-ethylcarbodiimide methiodide;1-(3-dimethylaminopropyl)-3-ethylcarbodiimide;1-cyclohexyl-3-(2-morpholinoethyl) carbodiimidemetho-p-toluenesulfonate; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimideand the like. EDC can catalyze a reaction in water over a wide pH range.The pH range may vary from 1 to 9. Most preferred pH range is 5 to 7.The desired pH may be achieved by using a biocompatible bufferingagents. The preferred buffers that can be used include, but not limitedto, phosphate buffered saline (PBS)(pH 7 to 7.5), morpholinoethanesulfonic acid (MES) (pH 5.5 to 6.5) and triethanol amine buffer(pH 7 to 7.5), sodium acetate buffer and the like. A bufferconcentration in the range of 10 mM to 100 mM is preferred. Among thebuffers, PBS or MES buffers are most preferred.

In one embodiment of the invention, a co-catalyst that may acceleratethe reaction between carbodiimide and iodinated derivative, is added.Examples of such co-catalyst include, but not limited to,n-hydroxysuccinimide or n-hydroxysulfosuccinimide. The molarconcentration of co-catalyst is in the same range as that of iodinatedcompound being reacted. The cross-linking reaction is generallycompleted with in 1 to 600 minutes, more preferably between 1 to 30minutes. The preferred reaction temperature is 0 to 45° C. Reaction at 4to 37° C. temperature range is even more preferred. If necessary,additives that control the properties of modified polymer, such asplasticizers, coloring agents and viscosity modifying, agents, andfillers such as calcium appetite that do interfere with the polymermodification reaction may be added.

The biodegradation of protein based cross-linked gels such as albumin orcollagen based gels occurs by an enzymatic pathway. If necessary, thenaturally occurring proteases enzymes such as trypsin, collagenases,pepsin and the like may be added during cross-linking and/or iodinemodification reaction. A bioactive compound may be added before themodification reaction, or are loaded via diffusion process inside themodified/cross-linked natural polymer.

The reaction conditions such as concentration, temperature, pH arecontrolled to obtain a desired iodine content in thecross-linked/modified polymer network. In various embodiments of theinvention, the desired iodine content of the modified polymer isadjusted to provide sufficient contrast in medical X-ray imagingapparatus. Alternatively two or more iodinated compounds may be used toachieve a desired iodine level. For example, Iopamidol, which has onlyhydroxy functional groups is used to modify acid functional groups inalbumin. Acid functionality of 3,5-bis(acetylamino)-2,4,6-triiodobenzoicacid is used to modify amine functional groups in the albumin. Theconcentration of total organic iodine in the modified polymer suitablefor X-ray imaging range may range from 30 mg/g to 300 mg/g of drycross-linked polymer. The most preferred iodine concentration range is50 mg/g to 200 mg/g of dry cross-linked polymer. Even more preferredrange is 50 to 150 mg/g of dry cross-linked polymer.

In one exemplary approach, 330 mg of bovine serum albumin was weighedand transferred in 50 ml polypropylene centrifuge tube. 2 ml iopamidolsolution (300 mg/g of iodine, Isovue-300 X-ray contrast agent) was addedto the tube and was transferred to refrigerator for complete dissolutionof albumin in the iopamidol solution. To this solution, 0.2 gn-hydroxysuccinimide and 0.336 g 1-ethyl-3-(3-dimethylaminopropylcarbodiimide) hydrochloride (EDC) were added. After completedissolution, the reaction mixture was transferred to a refrigerator.After 48 hours, the solution transformed into cross-linked hydrogel. Thehydrogel was washed with 10 ml phosphate buffered solution 2 times toremove unreacted reactants from the cross-linked gel. The gel wassubjected to x-ray imaging. The albumin hydrogel was clearly visible indeveloped X-ray film.

In some embodiments, the activation of hydroxy group andmodification/cross-linking is done simultaneously. FIG. 5 illustratesone exemplary embodiment in which albumin was reacted with iopamide inpresence of EDC as a catalyst and n-hydroxysuccinimide (NHS) as aco-catalyst. EDC promotes cross-linking of albumin as well as couplingof iopamidol Ito the albumin. The reaction is carried out in a MES or aPBS buffer for 4-24 hours at PH 5.5 to 7.5. The gel is washed to with aPBS buffer to remove unreacted iopamidol from the cross-linked gel. Thereaction variables such as time, temperature, concentration, andpressure are controlled in such a way that 1 to 100 percent primaryamine groups and/or acid groups on the protein are modified. Morepreferably, 10 to 95 percent reactive groups are modified, even morepreferably 40 to 95 percent reactive groups are modified. Thecross-linked or modified protein is washed to remove soluble unreactedfragments and may be used for implantation or as an absorbable biopsymarker.

In another embodiment of the invention, hyaluronic acid basedradio-opaque compositions is made by dissolving hyaluronic acid inIsovue-300 (lopamidol solution with 30% organically bound iodine)solution at 1-3% concentration. The esterification reaction betweenhydroxy group of lopamidol in Isovue and acid group of hyaluronic acidis promoted by the use of EDC as catalyst and n-hydroxysuccinimide asco-catalyst. The radio-opaque hyaluronic acid solution may be used inapplications where hyaluronic acid solutions are used. For example,radio-opaque hyaluronic acid may be more useful in accurate placement ofthe hyaluronic acid when injected between the knee joints.

In another embodiment of the invention, amine groups of chitosan arereacted with 3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid using EDC asa water soluble catalyst and n-hydroxysuccinimide as co-catalyst.

It will be obvious to a person skilled in the art that collagen andgelatin may be modified using a similar reaction conditions as albumin.In one exemplary approach, bovine pericardial tissue that containscollagen as its main constituent, elastin, and glycosaminoglycans ismodified using EDC and iodinated compound. Ten pericardium pieces, cutfrom a freshly obtained bovine pericardial sac, are reacted in 100 mMMES buffer (pH 6.5), with 3,5-bis(acetylamino)-2,4,6-triiodobenzoicacid, iopamidol, EDC and n-hydroxysuccinimide for 48 hours. Foradditional iodine incorporation, the tissue is further reacted withIopamidol solution with 30% organically bound iodine using EDC ascatalyst and NHS as cocatalyst. The modified tissue is separated andimaged using x-ray imaging technique. Modified tissue with 30 mg/g to200 mg/g of iodine relative to dry tissue weight is preferred.

EDC cross-linked natural polymer degrades the iodine modifiedradio-opaque natural polymer into non-toxic amino acid constituents andiodinated compounds such as Iopamidol with known safety profile. Boththe amino acid and iodinated compounds are safely eliminated by the bodyupon degradation.

In various embodiments of the invention, bioactive compound is added tothe radio-opaque natural polymer hydrogel for localized therapeutictreatment. The amount of bioactive compound in the composition may bedependent on local disease being addressed, solubility of compound inthe composition and toxicology of the compound. The bioactive compoundmay be added from 0.1% to 30% w/w of total composition. A range of 1 to10% is even more preferred. Those skilled in controlled drug deliveryart will recognize that many changes could be made to achieve adesirable therapeutically effective dose and release of bioactivecompound from the cross-linked radio-opaque natural polymer hydrogelcould be made. Such changes are considered to be a part of thisinvention.

In one embodiment of the invention, 1 gram of radio-opaque albuminhydrogel prepared as described previously is incubated in 10 mg/mlpaclitaxel solution dissolved in ethanol for 24 hours. The paclitaxeldiffuses inside the radio-opaque hydrogel in 24 hour. The hydrogel isremoved from the paclitaxel solution, washed with 10 ml PBS solution 2times to remove surface bound paclitaxel. Alternatively, paclitaxelcould be added and suspended in albumin solution prior to cross-linkingreaction. The release of paclitaxel from cross-linked hydrogel ismonitored for 7 days by incubating the hydrogel in 3 ml PBS solution at37° C. and exchanging it periodically with fresh PBS. The concentrationof paclitaxel eluted in the PBS solution is analyzed by high performanceliquid chromatography. A controlled release of paclitaxel from thecross-linked radio-opaque hydrogel is observed. The release profile ofpaclitaxel from cross-linked radio-opaque hydrogel may be controlled bychanging variables such as paclitaxel concentration, the incubationmedium, the cross-linked density of radio-opaque hydrogel, and the like.

In various embodiments of the invention, albumin, EDC, NHS, bufferingagent and iodinated compound such as Iopamidol are packaged as a kit andused as injectable cross-linkable radio-opaque formulation. All theseconstituents may be premixed just prior to surgical procedure or mixedin situ using a multi-lumen device such as multi-lumen catheter andinjected using MIS surgical technique. For example, such mixture mayserve as injectable biodegradable surgical/breast biopsy marker or drugdelivery device.

A prefabricated cross-linked radio-opaque albumin or protein that isporous in nature may be useful as surgical biopsy marker. The porositymay be created by many methods known in the tissue engineering scaffoldpreparation art. On one exemplary embodiment, a cross-linked albuminhydrogel is prepared by reacting iopamidol and albumin in presence ofEDC and n-hydroxysuccinimide in water. The water from the crosslinkedhydrogel is removed by lyophilization. The removal of water creates aporosity, which filled with air which makes it visible in ultrasonicimaging technique. Air in the porous structure may be replaced withother biocompatible gases such as oxygen, carbon dioxide and the like.Low boiling liquids which form high vapor pressure at body temperature(37° C.) may also be used. These include compounds like fluorinatedhydrocarbon based liquids. The total porosity may vary from 20% to 95%of the volume of the implant, more preferably from 50% to 90% of theimplant.

In another embodiment of the invention, 1 g of gelatin, 1 g of iohexyland optimally a magnetic resonance imaging agent (0.25 g) are dissolvedin 20 ml phosphate buffered saline. The mixture is poured into a moldand lyophilized to form a porous gelatin sheet. The porosity of spongealong with its entrapped air provides visibility in ultrasonic imagingapparatus while iohexyl and magnetic imaging agent provide visibility inmedical x-ray imaging technique and magnetic resonance imaging techniquerespectively. The sponges is cut into small 5 mm circles and spraycoated with polylactide-polyglycolide polymer dissolved in chloroform.The coating is applied from all sides of the foam. Upon evaporation ofchloroform, the biodegradable polymer coating is formed on the outsideof foam (skin formation). This coating limits the access of water to theimaging agents incorporated in the foam thereby preventing theirdiffusion from the foam. Upon implantation and subsequent degradation ofthe outside coating, the gelatin foam and its imaging agents are safelyeliminated from the body. The imaging agents in the foam providevisibility in x-ray imaging, magnetic resonance imaging and ultrasonicimaging. This visibility in multiple imaging techniques is useful formany minimally invasive surgical techniques including surgical biopsy.

In another embodiment, ionic contract media such as Diatrizoic acid,sodium salt solution is mixed with cationic polymer such as polylysineor chitosan. The anionic salt forms an ionic bond to the cationicpolymer such as chitosan or polylysine. Such ionically bound polymericmedia can be used as an injectable biopsy marker or for drug deliveryuse. The mixing of anionic contrast media and cationic polymer may beperformed in situ to form a gel in situ.

FIG. 6 illustrates exemplary modification scheme for modification ofnatural polymer such as albumin or antibody using iodinated compound toproduce a substantially non-crosslinked water soluble modified polymer.Activated ester n-hydroxy ester of diatrizoic acid capable of reactingwith amino group is protein is prepared by reaction of diatrizoic acidwith n-hydroxysuccinimide using dicyclohexylcarbodiimide (DCC) as acatalyst in an organic solvent such as dimethyl formamide. Uponisolation and purification of the ester using column chromatography, itis then used in subsequent reaction with protein. The protein solutionsuch as albumin at concentration of 2 to 20% in phosphate buffer pH 7.2is reacted with diatrizoic acid NHS ester (2-3 molar excess relative toamine group concentration in albumin) at room temperature for 18 hoursto form iodinated albumin derivative. The NHS derivative and other smallmolecular weight compounds are removed by dialysis using 10000 Daltonmolecular weight cutoff dialysis membrane. The dialyzed protein solutionis lyophilized to isolate the protein.

Radio-Opaque Contrast Media

In various embodiments of the invention, an oligomeric or polymericpolyether chain is linked to a non-polymeric iodinated moiety through abio stable bond. The radio-opacity of these compounds allows them to beeasily traced within the human or animal body thereby enabling their useas contrast media in medical imaging and for localized drug deliveryapplications.

FIG. 7 shows the three structural components of the disclosedradio-opaque compound; the first part (part A) comprises at least oneoligomeric or polymeric polyether chain, the second part (part B)comprises at least one non-polymeric iodinated moiety and the third part(part C) comprises one or more hydrolytically stable chemical bondlinking part A and part B. The chemical bonds in the three parts arestable when stored in an aqueous environment. In various embodiments ofthe invention, the combined molecular weight of the three parts of thecompound is within 400-30000 Daltons range, more precisely it is between1000 to 20000 Daltons range and even more precisely in the range of 2000to 18000 Daltons. In addition, the solubility of the disclosed compoundsis at least 1 g/100 ml in an aqueous solution. Typically watersolubility of above 1% is believed to be most useful to remove thecompound safely from the body. In various embodiment of the invention,the radio-opaque compound is in a liquid state in a temperature range of10° C. to 45° C.

FIG. 8 illustrates exemplary structures that form part A of theradio-opaque compound. In various embodiments of the invention, Part Ais a polyether oligomer or polymer, such as polyethylene glycol (PEG),polyethylene oxide (PEO), or polypropylene oxide (PPO), polyethyleneoxide-polypropylene oxide-polyethylene oxide block copolymer,polypropylene oxide-polyethyleneoxide-polypropylene block copolymer, ora derivative of such compounds. Further, the polyether region of Part Amay be a single chain or a combination of multiple chains linked througha chemical bond to the iodinated moiety (part B). Part A may have one ormore terminal groups. For example, the polyether chain may be linearwith two terminal group, or may be branched, star or dendramer with morethan two terminal groups. The molecular weight of part A is in the rangeof 400 to 20000 Daltons. Molecular weight below 400 makes theradio-opaque compound substantially insoluble in water and renders thecompound unsuitable for a number of medical applications. In addition,molecular weight above 20000 Daltons is also not suitable because suchhigh molecular weight makes the compound difficult to remove from thehuman body. The polyether chain contains at least 70% PEG or PEO byweight. Other polyethers such as polypropylene glycol are insoluble inwater at body temperature. PEG content of above 70% makes it soluble inwater. In case of multiple chains, the combined molecular weight rangeof the polyether chain is within a range of 400 to 20000 Daltons.

FIG. 9 illustrates exemplary structures of part B of the radio-opaquecompound disclosed in the invention. In various embodiments of theinvention, the iodinated moiety is a low molecular weight non-polymericiodinated compound/radical. Examples of such compounds includesubstituted benzene ring compounds like triiodobenzene,1,2,3-triodobenzoic acid, 2,4,5-triodobenzoic acid, triiodobenzylalcohol, 3-aminotriodobenzene, iodinated xanthene derivatives such asRose Bengal, Erythrosine and their derivatives. In various embodimentsof the invention, the iodinated moiety is non-ionic. The non-ionicnature of the iodinated moiety does not change osmolarity of aqueoussolutions of the radio-opaque compound.

FIG. 10 illustrates examples of hydrolytically stable chemical bonds(part C) of the radio-opaque compound disclosed in the invention. Invarious embodiments of the invention, the iodinated moiety (IM) islinked to the polymeric chain (PE) by a hydrolytically stable chemicalbond. Examples of such hydrolytically stable bonds include:carbon-carbon, carbon-oxygen (ether) and carbon-nitrogen (amide), andcarbon-sulfur bonds. Ester and urethane bonds are least preferred due totheir hydrolytic instability in an aqueous environment.

Example: In various embodiments of the invention, PEG based radio-opaquecompounds with degradable ester links are synthesized. In anotherembodiment, the compound showed significant degradation (loss of iodinemoieties) with 60 day incubation. The stability of the compound wasmonitored in PBS (pH 7.2) at 37° C. for 30 days. The terminal iodinegroups were analyzed by UV spectrophotometer. Therefore polyethyleneglycol based radio-opaque compounds containing ester group such asglutarate or succinate are unsuitable for long-term storage in aqueoussolutions.

FIG. 11 illustrates exemplary structural arrangements of theradio-opaque compounds disclosed in the invention. In variousembodiments of the compound, the polymeric chain is terminated with oneor more iodinated end-groups. Example A illustrates a linear polyetherchain with a single iodinated moiety attached at the terminal end of thechain. B illustrates a linear polyether chain where both the ends areterminated with iodinated moieties. C illustrates a three-arm polyetherchain whose ends are terminated with iodinated moiety. D and Eillustrate compounds where one iodinated moiety is linked to two andfour polyether chain respectively. E and F illustrate 4-arm and 8-armbranched polyether chains respectively, with each arm of the chainterminated with an iodinated moiety. H illustrates an 8-arm polyetherchain where only seven ends of the polyether chain are terminated withiodinated moieties and one end is terminated with other moieties.Examples of such moieties include compounds that may be useful in MRIimaging such as ligands containing gadolinium atoms or an antibody thatmay help to accumulate the radio-opaque compound in an antibody-specifictissue.

Different structural arrangements of the radio-opaque compounds resultin compounds with different physical properties such as watersolubility, iodine content, melting point, and viscosity. Table 2describes properties of some compositions.

TABLE 2 Properties of polyether based contrast agents No. of Iodine Avg.end- atoms Polyether Mol. wt. Linking groups per Iodine Code (PE) of PEIodinated Moiety Group modified molecule (%) P101 PEG 400 400Triiodobenzoic acid Ester 2 6 56 P102 PEG 600 400 Triodophenol Ester 2 650.6 diacid P103 PEG 1000 Triodophenol Ether 1 3 27 1000 P105 PEG 1000Triiodobenzoic acid Ester 3 9 47 1000 triol P104 PEG 1000 ErythrosinEster 2 8 37 1000 P105 PEG 1000 Triiodobenzoic acid Ester 2 6 39 1000diol P106 PEG 2000 Triiodobenzoic acid Ester 1 3 15 2000 monomethoxyP107 PEG 2000 Triiodobenzoic acid Amide 2 6 26 2000 amine P108 PEG 10000Triiodobenzoic acid Ester 8 24 22 10000 8 arm P109 PEG 20000Triiodobenzoic acid Amide 8 24 13 20000 8 arm amine P110 Pluronic 8000Triiodobenzoic acid Ester 2 6 9 F68

Star PEG polymers with 8 arms terminated with a triiodobenzene moietyhas 24 iodine atoms per molecule and if terminated with erythrosine has32 iodine atoms per molecule. A large concentration of iodine atoms permolecule provides better visibility in medical imaging, and allows theuse of less concentrated solutions of the compositions disclosed inmedical imaging to obtain images with high resolution.

Different tissues in the human body, based on their chemicalcomposition, scatter/absorb/transmit different amount of X-rays andthereby produce an image in the detector. The radio-opaque compounds ofthe invention can be infused exogenously such that it gets distributedin the tissues to be imaged. The infused compound preferentially absorbsx-rays in the tissue and therefore improves quality of the image. Suchimproved image results in better diagnosis of the medical condition.Such compounds that help in imaging of tissues are better known ascontrast agents.

In various embodiments the radio-opaque compounds provided by theinvention can be synthesized by different synthetic methods known in thepolyethylene glycol modification chemistry art. FIG. 12 illustrates anexemplary method for synthesis of the radio-opaque compound provided bythe invention. The example shows synthesis of a compound having one endof the polyether chain terminated with an iodinated moiety.Triiodophenol (A) is used to initiate the polymerization of ethyleneoxide (B) using organometallic catalyst to obtain a linear PEG basedradio-opaque compound (C). This is a typical ethoxylation modificationof alcohol group known in the ethylene oxide polymerization art. Themolecular weight of PEG is limited to 1000 Daltons by controlling themolar ratio of ethylene oxide to phenol ratio (molar ratio 22). Thismolecule has one iodinated moiety per chain and the other chain end isterminated with a hydroxyl group.

FIG. 13 illustrates another exemplary method for synthesis ofradio-opaque compound of the invention by modifying the terminal ends ofPEG. In various embodiments of the invention the radio-opaque compoundsare synthesized by modifying the two terminal ends of commerciallyavailable PEG (A), by esterification with triiodobenzoic acid (B). Inone embodiment, DCC is used as a catalyst to assist the esterificationreaction.

In another embodiment of the invention, a radio-opaque compound issynthesized using a commercially available amine terminated polyethyleneglycol (Jeffamine®) and triiodobenzoic acid using DCC as catalyst. Thecompound has approximately 25% iodine.

In another embodiment of the invention, a radio-opaque compound is anerythrosine terminated polyethylene glycol. Erythrosin has 4 iodineatoms per molecule. Therefore, this molecule has 8 iodine molecules permolecule.

In another embodiment of the invention, an 8 arm amine terminated PEG20000 is reacted with triiodobenzoic acid to obtain a radio-opaquecompound with 24 iodine atoms per PEG chain, linked at each terminalend, through an amide linkage. The amine terminated polymers areavailable commercially for example Jeffamine can be purchased fromAldrich or from Huntsman Inc. Amine terminated PEG can also besynthesized using methods in the polymer synthesis art.

In another embodiment of the invention, PEG of molecular weight 600having two terminal hydroxyl groups is reacted with triiodophenol usingDCC as a catalyst. The reaction results in a radio-opaque compound withPEG of molecular weight 600 as Part A, triiodobenzene as Part B and anester linkage as part C. Both the ends of the PEG are substituted withiodinated moiety and the compound is liquid at room temperature.

In various embodiments of the invention, similar ethoxylation chemistryor other known methods of ethylene oxide polymerization known to thoseskilled in the polymer synthesis art are used to introduce PEG chains onnon-ionic iodinated moieties like iohexyl, metrizamide, iopamidol,iopentol, iopromide, ioversol by their ethoxylation. The introduction ofPEG chains on non-ionic iodinated moieties such as iohexyl improveshemocompatibility of such moieties and reduces their interaction withblood proteins. The high molecular weight achieved as a result ofethoxylation is also helpful in reducing number of particles. Increasein molecular weight results into less number of particles in thesolution, (lower osmolarity).

In various embodiments of the invention, the terminal end groups of PEGchain after ethoxylation are reacted with functional monomers such asacryloyl chloride or methacryloyl chloride to obtain radio-opaquepolymerizable macromonomers. These macromonomers are water soluble dueto polyethylene glycol chain and can form radio-opaque hydrogels uponfree radical polymerization and cross-linking.

Radio-opaque compounds prepared according to disclosed exemplary methodsand their modifications are listed in Table 2 along with theircalculated iodine content. As can be seen from this table, compoundswith wide range of iodine contents, molecular weights, degree ofbranching can be synthesized.

In various embodiments of the invention, two different radio-opaquecompounds with different molecular weight but same Iodine content areobtained. A linear polyethylene glycol with molecular weight 2000terminated with triiodibenzoic acid has the same amount of iodine aspolyethylene glycol with molecular weight 8000 having 8 arms terminatedwith triiodobenzoic acid. The radio-opaque compound with high molecularweight polymer (8000) has substantially less number of particles inaqueous solution as compared to the radio-opaque compound with lowmolecular weight counterpart when dissolved at equal concentration(wt/v). Thus, high molecular weight polymer is useful in reducingosmolarity of the solution of radio-opaque compounds withoutcompromising on the iodine content.

In various embodiments of the invention, compositions of radio-opaquecompounds also contain, a buffering agent such as phosphate salts,triethanol amine, HEPES to maintain a pH in the range of 5 to 8,precisely in the range of 7 to 8 and more precisely in the range of 6.8to 7.5.

Table 3 lists ingredients of an exemplary aqueous compositions for X-rayimaging.

TABLE 3 Weight Component of composition Function (g) Jeffaminetriiodobenzamide X-ray absorbing polyether 40 component Triethanol amineBuffering Agent 0.15 Triethanol amine hydrochloride Buffering Agent 0.19Sodium chloride Osmolarity balancing agent 0.36 Distilled deionizedwater Solvent 59.30

Table 4 lists ingredients of an exemplary aqueous composition comprisingpolymeric and non-polymeric non-ionic contrast agents.

TABLE 4 Weight Component Function (g) Jeffamine triiodobenzamide X-rayabsorbing 28 polymeric component Iohexol X-ray absorbing non- 43 ioniccomponent 20 mM triethanolamine buffer, Solvent 29 pH 7.2

Since many PEG based synthesis preparations frequently result in loss ofantioxidants present in the PEG raw material, the lost antioxidant mustre-added in the final formulation to improve shelf life and stability ofPEG molecules. In various embodiments of the invention, antioxidants ofare added in very small amounts to the composition, typically in therange of 0.0001% to 2% and precisely in the range of 0.005% to 0.1%percent. Examples of antioxidants that are added includebutylatedhydroxy toluene (also known as BHT or2,6-di-tert-butyl-4-methylphenol), butylatedhydroxy anisole (BHA),hydroquinone, vitamin E or any other suitable antioxidants known in thepharmaceutical dosage preparation art.

Concentrated aqueous solutions of PEG containing compositions describedin this invention may have tendency to form foam during routine handlingof the solution. In various embodiments of the inventions, defoamingagents are added; to reduce the amount of foam formation. Examples ofsuch defoaming agents include fatty acid alcohols, aliphatic long chainalcohols, octanol, 1,2-octanediol, decanol, silicone fluids etc. Theantifoaming agents are added in the range of 0.0001 to 2%, moreprecisely in the range of 0.001 to 0.1%.

Table 5 provides exemplary aqueous compositions for X-ray imagingcomprising antioxidant, de-foaming agent, and viscosity reducing agent.

TABLE 5 Weight Component Function (g) Jeffamine triiodobenzamide X-rayabsorbing polyether 32 component Triethanol amine Buffering Agent 0.15Triethanol amine hydrochloride Buffering Agent 0.19 Sodium chlorideOsmolarity balancing agent 0.36 Distilled deionized water Solvent 67.31-octanol De-foaming agent 0.02 BHT Antioxidant 0.005 Ethanol Viscosityreducing agent 8

FIG. 14 illustrates the self-assembly property of the radio-opaquecompounds in aqueous medium. In various embodiments of the invention,the iodinated moieties (A) linked to polyether chain (B) self assemblein an aqueous environment. The formation of iodine rich hydrophobicdomains in water leads to localized high concentrations of iodineproviding better contrasting properties at low iodine concentration. Thecarbon-oxygen bond in PEG or polyether chain permits free rotation alongthe carbon-oxygen axis. In aqueous environment, the rotationalflexibility permits the polyether chain ends to retain mobility.

In an embodiment of the invention where the iodinated moiety istriiodobenzene, the planar structure of triiodobenzene ring and its highhydrophobicity results in iodine rich hydrophobic domains when dissolvedat high concentrations in water, typically above 0.1% percent wt/v. Suchdomains have very high iodine content (as the iodine content oftriiodobenzene ring is 84 percent) and attenuate the x-rays with highefficiency, thereby improving contrast properties in medical x-rayapplication.

The contrast media compositions described in various embodiments of theinvention can be used for medical imaging applications. The list of suchapplications includes but is not limited to: intravascular use;angiography, urography, phlebography and CT-enhancement; subarachnoiduse: lumbar, thoracic and cervical myelography and in computedtomography of the basal cisterns; body cavities: arthrography,endoscopic retrograde cholangiopancreatography (ERCP) andpancreatography (ERP), herniography, hysterosalpingography andsialography.

The radio-opaque compounds described above can be combined withphysiologically acceptable carrier media to form various contrast agentcompositions and pharmaceutical compositions.

The pharmaceutical compositions can be used for localized drug deliveryapplications. Such compositions contain a bioactive compound dissolvedin the hydrophobic domains of radio-opaque compound. The bioactivecompounds can be released in a controlled manner in human or animalbody.

The formation of self-assembly largely depends on temperature, pH,carrier medium, molecular structure (terminal versus non-terminal), typeof iodinated moiety and molecular weight of PEG chain.

Compositions self assembled between 15-45° C., more preferably between25 to 37° C. are preferred. Self assembly in aqueous environment suchphysiological pH 7.2 is even more preferred. It is recognized that selfassembly property is very specific to carrier used and organic solventssuch as chloroform are not useful for self assembly formation andtherefore cannot be used. For self assembly, PEG molecular weightbetween 600 to 30000 Daltons per IM moiety is preferred; PEG withmolecular weight 1000 to 20000 Daltons is even more preferred.

In various embodiments of the invention, the self-assembly is furtherassisted by adding hydrophobic compounds to the aqueous solution ofradio-opaque compounds. Example of such hydrophobic compounds includelong chain alcohols, naturally occurring fatty acids, triiodobenzoicacid, Erythrosin, iohexyl, metrizamide, iopamidol, iopentol, iopromide,and Ioversol, octanol, 1-8-octanediol, 1,2-octanediol, oleic acid,steric acid, vitamin E, vitamin E acetate, and vitamin E modified withpolyethylene glycol.

In various embodiments of the invention, the hydrophobic compounds arebioactive compound such as paclitaxel or Lovastatin. These compounds areadded in various proportions depending on their solubility, iodinecontent and toxicological profile. Such compounds are added precisely inthe range of 0.1% to 70% range, more precisely in the range of 1 to 50%,even more precisely in the range of 5 to 30%.

In various embodiments of the invention, the self-assembly behavior ofthese radio-opaque compounds is exploited to deliver bioactive compounds(dissolved in the hydrophobic domains) in human or animal body. Thebioactive compounds are released in a controlled manner. In oneembodiment, paclitaxel dissolved in ethanol is added to 30 percentaqueous solution of PEG 8-arm triiodobenzamide. The solution is filteredto remove unsolubilized paclitaxel. The paclitaxel dissolved compositionis used as a contrast agent as well as a controlled drug deliveryvehicle. In another embodiment, such composition is used to deliverpaclitaxel at the site of angioplasty to control restenosis.

In various embodiments of the invention, ionic and non-ioniccompositions of radio-opaque compounds with 50-500 mg l/g Iodinecontent, more precisely 140-400 mg l/g are used in medical x-rayimaging.

In various embodiments of the invention, some compositions containingthe radio-opaque compounds exist as neat liquids, which may be directlyinjected and used as contrast agents. Liquids have an advantage oversolutions that they can be used without any solvent such as water. Wateris also a reactive solvent and can cause hydrolysis of the contrastagent. Elimination of water can improve storage stability. Since pureliquids do not have any solvent, they also can have high iodine contentthat results into better x-ray image quality. Liquids also can be filtersterilized which can simplify manufacturing process. Removal ofsolvents/water from formulation also reduces the osmolarity of the finalformulation as the dissociation of molecules in water results into highosmolarity.

In various embodiments of the invention, the compositions existing asneat liquids are used as solvents for ionic/non-ionic contrast mediacompounds or for bioactive compounds. Examples of such compounds includeIohexyl, Metrizamide, iopamidol, iopentol, iopromide, triiodobenzoicacid, Erythrosin and loversol. These compounds are mixed with thecompositions of the invention in the range of 0.1 to 90 percent,precisely in the range of 1 to 30 percent. Various properties of thesecompositions (such as percent iodine content, viscosity, cost) can becontrolled by adding mixtures. Examples of such mixtures include organicbuffering agents such as triethanol amine, HEPES, and viscositycontrolling agents such as ethanol, polyethylene glycol, glycerol,1,2-propane diol, 1,4-octanediol, 1-5 pentane diol, isopropanol,n-methylpyrrolidinone and dimethyl sulfoxide.

Table 6 describes one such example of a contrast agent dissolved in aneat liquid composition containing the radio-opaque compound.

TABLE 6 Weight Component Function (g) PEG 1000 X-ray absorbing polyether85 triiodobenzamide component Ethanol Viscosity modifier 15

In various embodiments of the invention, ionic or non-ionic iodinatedcontrast media compounds used in current clinical practice such asiohexyl, metrizamide, iopamidol, iopentol, iopromide, and loversol aremixed with commercially available biostable biocompatible polymers suchas polymers used in fabrication of long term (typically more than sixmonths) implantable medical devices to obtain a polymer. Examples ofpolymers used in fabrication of long term implantable medical devicesinclude polyesters such as polyethylene terephthalate, polyethylene,polyurethanes such as polycarbonate polyurethanes, polyetherpolyurethanes, polytetrafluoroethylene (Teflon), polypropylene,polymethacrylates such as polymethyl methacrylate or polybutylmethacrylates, ethylene vinyl acetate copolymer or their derivatives,fixed animal tissues such as glutaraldehyde fixed tissue, siliconerubber and the like. The blending can be carried out using variety oftechnique known in the polymer/rubber processing art such as solventbased methods, melt based methods.

In various embodiments of the invention, compositions containing ionicand non-ionic contrast agents such Metrizamide, iopamidol, iopentol,iopromide, and loversol in non-aqueous medium are disclosed. Thenon-aqueous medium offers a unique way to control ionization of contrastagents. Use of non-aqueous organic medium prevents ionization thereforeeliminating side effects associated with the ionization. Anotheradvantage of organic solvents is that they may permit the use ofcontrast agents that are unstable in aqueous solutions. 1 to 90 percentsolutions of Metrizamide, iopamidol, iopentol, iopromide, and loversolin biocompatible organic solvents are used. Examples of non-aqueoussolvents that can be used are polar solvents like n-methylpyrrolidinone,dimethyl sulfoxide; alcohols such as ethanol, isopropanol, 1,3-propanediol, 1,4-butane diol, glycerol; polyethylene glycol and fatty acidssuch as oleic acid. A mixture of these solvents in any proportion may beused. In some cases water can be used as a cosolvent.

Table 7 lists ingredients of an exemplary non-aqueous based contrastmedia composition.

TABLE 7 Weight Component Function (g) PEG 1000 X-ray absorbing polyether80 tribenzoacetamide component Ethanol Non-aqueous solvent 10 N-methylpyrrolidinone Non-aqueous solvent 10

In another embodiment of the invention, iodinated compound such asIohexyl or 3,5-Diacetamido-2,4,6-triiodobenzoic acid and high molecularweight ethylene vinyl acetate copolymer//butyl methacrylate copolymerare mixed in the organic solvent such as dimethyl sulfoxide orchloroform. The solvent is removed to form a film. The polymeric film isradio-opaque when viewed using medical x-ray imaging equipment. Sincemany biocompatible polymers such as polyesters, polyethylene,polyurethanes, polytetrafluoroethylene (Teflon), polypropylene,polymethyl methacrylate, ethylene vinyl acetate copolymer, siliconerubber and Iohexyl have proven history of human use, the devices willface relatively less regulatory scrutiny. Alternately, iodinatedcompositions described in this invention may also be physically mixed orblended to produce a radio-opaque biostable device.

The iodinated compound physically mixed with the biodegradable orbiostable polymer may be completely soluble in the polymer matrix or mayexist as separate phase. The phase separation will depend on themolecular structure of the polymer and iodinated compound used. In aheterogeneous mixture of iodinated compound and polymer matrix, theiodinated compound size may range from 50 nm to 1000 microns dependingon the method of preparation and polymer/iodinated compound molecularstructure. The preferred size of iodinated compound in the compositematrix is 0.1 to 200 microns. Alternatively, iodinated compound may befirst obtained in a particular size of interest and then dispersed inthe polymer matrix. Many methods known in the drug delivery dosagepreparation art may be used to prepare an iodinated compound ofparticular size. In one exemplary method, commercially availableiodinated compounds such as metrizamide or sodium diatrizoate dihydratemay be cryogenically ground and sieved using standard mechanicalsieves/meshes. The fraction of particles having a size in between 100and 200 microns is collected and used in preparing polymer-iodinatedcompound mixture. The iodinated compound particle shape may bespherical, cylindrical, cubical, irregular and the like.

Some of the biodegradable and biostable radio-opaque compositionsdescribed in this invention may be optically transparent orsemi-transparent (transparent in the visible spectrum of light from 400to 800 nm) due to solubility of iodinated compound in the polymer matrixand the transparent nature of polymer used. Such compositions may beuseful to form transparent and radio-opaque medical devices such asangioplasty catheters or as transparent and radio-opaque coatings formedical devices. Polyurethane, polylactones and acrylic basedtransparent and radio-opaque compositions and coatings are especiallypreferred.

In another embodiment of the invention, a non-polymeric liquid carriersuch as sucrose acetate is mixed with iodinated compounds such asMetrizamide, iopamidol, iopentol, iopromide, and Ioversol to make itradio-opaque.

Water is not a very good solvent for PEG based compositions described inthis invention. Use of non-aqueous compositions is also very useful incontrolling viscosity of final composition for medical imaging.Polymeric contrast media generally have high viscosity. This viscositycan be reduced by adding biocompatible organic solvents. Whennon-aqueous compositions are introduced in the aqueous environment, suchas physiological environment, the PEG based compositions may temporarilyform water swollen hydrogels that, will dissolve as they are furtherdiluted away. Such temporary gel formation may be helpful in improvingcontrasting properties at the site of injection.

Thermosensitive Gels

The present invention also provides radio-opaque compositions thatundergo gelation due to physical cross-linking and/or change intemperature. In one exemplary embodiment, a block polyether copolymer(Pluronic F127) that shows thermoreversible gelation in water and awater soluble iodinated compound are dissolved in PBS solution. PluronicF127 is dissolved in commercially available X-ray contrast agentsolution to produce a 30% Pluronic F 127 in Isovue solution. When thePluronic-Isovue solution is cooled to 15° C. or below, the solution isobserved to be free flowing and could be injected using a syringe. Whenthe same solution is warmed to body temperature (37° C. or above), it istransformed into a non-fluid hydrogel. The gelled solution may also beinjected as a paste. The Pluronic-Isovue solution in fluid state as wellas in gel state is visible in X-ray imaging apparatus. In variousembodiments of the invention, the Pluronic-Isovue solution may be addedwith bioactive compound to produce local therapeutic effect. In thepresent invention polymers that show thermoreversible gelation and thatcan be used safely inside the body are preferred. The polymers may bebiodegradable or bio-inert. The preferred polymers, their derivativesand analogs include, but are not limited to: PEO-PPE-PEO blockcopolymers (Pluronic surfactants from BASF), PPO-PEO-PEO blockcopolymers (Reverse Pluronics), Tetronics copolymers:PEO-polylactone-PEO and polylactone-PEO-polylactone block copolymers,PEO-polyhydroxy acid-PEO, polyhydroxyacid-PEO-polyhydroxy acid,PEo-polyhydroxy acid, PEO-polycaprolactone copolymers, gelatin and thelike. Some gelatin derivatives and PEO-polylactone-PEO, andpolylactone-PEO-polylactone block copolymers show gelation when theirwarmed aqueous solutions (temperature 37 to 55)° are cooled to bodytemperature. When aqueous solutions are warmed to 45° C. or above, uponcooling, the solution of these derivatives turns into a non-fluidhydrogel. The concentration of polymer in water will depend on thepolymer chosen. For example, polymers like Pluronic F127 showthermoreversible gelation at 10 to 50% concentration range, morepreferably 20-30% concentration range. A concentration where polymershows thermoreversible gelation around body temperature is mostpreferred.

The iodinated compound provides radio-opacity to the thermoreversiblegel. The preferred iodinated compounds are water soluble and with threeto four iodine atoms per molecule. The preferred iodine compoundsinclude, but not limited to, iohexyl, metrizamide, iopamidol,3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid, meglumine diatrizoate,iopentol, iopromide, triiodobenzoic acid, erythrosine and ioversol andtheir derivatives. The iodinated compound is added in sufficient amountto produce a good quality image in medical X-ray image apparatus. Thepreferred amount of organically bound iodine in the solution or gel mayrange from 3 percent to 40 percent, more preferably 10 to 20 percent.The amount of iodine used may vary depending on the medical X-rayimaging technology used. The newer machines with better detector needsmall amount of iodine content to form a good image. Additionaladditives such as biocompatible coloring agent may be added to thecompositions described above to improve visibility during open surgery.In addition, an antioxidant may be added to improve shelf life and thelike.

In various embodiments, the iodinated compounds are chemically bound tothe polymer that shows thermoreversible gelation. In one exemplaryembodiment, Pluronic F68 copolymer that shows thermoreversible gelationis reacted with triiodobenzoic benzoic acid using DCC as a catalyst. Themodified polymer isolated and redissolved in water to form aqueoussolution. Concentrated aqueous solution of triiodo ester of PluronicF127 (typical concentration >20%) display thermosensitive gelationbehavior. In addition, additional iodine containing compounds mentionedabove may be added to increase iodine content of the polymer.

In various embodiments of the invention, bioactive compounds are beadded to the thermosensitive composition for local therapeutic effect.The amount of bioactive compound in the composition may be dependent onlocal disease being addressed, solubility of compound in the compositionand toxicology of the compound. The bioactive compound may be added from0.1% to 30% w/w of total composition. A range of 1 to 10% is even morepreferred.

The biodegradable radio-opaque composition of the invention may beformulated such that it can be delivered using with Minimally InvasiveSurgical (MIS) techniques. Examples of such techniques include, but arenot limited to laparoscopy, thoroscopy and simple injection.

Such molded or tissue conformed polymers are applicable for medicalconditions where a temporary presence of biocompatible, biodegradablepolymeric devise is desired. Exemplary applications include, but are notlimited to prevention of postoperative adhesions, prevention of scarformation after laminectomy and the like

Hydrophobic Radio-Opaque Biodegradable Compositions

This invention also provides methods and compositions for makinginjectable hydrophobic radio-opaque biodegradable compositions.

In various embodiments, iodinated compounds such as ionic and non-ioniccontrast agents are mixed or blended with commercially availablepolymers such polylactones and polyhydroxyacids, and the biodegradableradio-opaque compound of the present invention. These ionic andnon-ionic contrast agents are used as a filler in biodegradablepolymers. Examples of ionic and non-ionic contrast agents include, butare not limited to triiodobenzoic acid, meglumine diatrizoate,diatrizoic acid salts, metrizamide, iopamidol, iopentol, iopromide, andIoversol. Typically, iodinated compounds are added in 1 to 90% rangemore typically from 5 to 70% weight range.

In another embodiment of the invention, biodegradable polymer and aniodinated compound are mixed with biocompatible organic solvent such asn-methylpyrrolidinone or dimethyl sulfoxide. The mixture is transportedto a surgical site and deposited inside the human body. The presence ofiodinated compound makes the composition visible under x-ray imagingequipment.

In another embodiment of the invention iodinated compound such asIohexyl and high molecular weight polyhydroxy acid or polylactidecopolymers are mixed in the organic solvent such as dimethyl sulfoxide.The solvent is removed to form a polymeric film. The polymeric film isradio-opaque when viewed using medical X-ray imaging equipment.

In another embodiment of the invention, the low melting triiodobenzoicacid terminated polymer and an antibiotic such as tetracycline isdeposited as a melt inside a periodontal cavity. The polymer solidifiesinside the periodontal cavity. The drug is then released in a sustainedmanner over a period of time. The drugs may be incorporated into fineparticles such as microspheres of hydrophobically and hydrophillicallyend-capped biodegradable polymers. Subsequently a dispersion of thesemicrospheres may be injected parenterally, subcutaneously andintramuscularly using suitable surgical technique. It will be apparentto a person skilled in the art that other methods of drugsadministration and controlled drug delivery may be envisaged.

In one preferred embodiment, a low melting biodegradable polymer isphysically mixed with a water soluble iodinated compound. The mixture isthen filled in an MIS delivery device and transported to a surgicalsite. The mixture is melted ‘in-situ’ and injected at the implant siteto fill a body cavity or void. The mixture solidifies in the bodycavity. The iodinated compound that remains entrapped in thebiodegradable polymers provides radio-opacity to the solidified implant.Upon degradation, the iodinated compound and the hydrolysis products ofbiodegradable polymer are safely removed from the body. Biodegradablepolymer with molecular weight 400 to 30000 g/mole may be preferred dueto their low melt viscosity. Molecular weight between 1000 to 10000g/mole is even more preferred. The preferred biodegradable polymers thatmay be used include, but not limited to: polymers, copolymers oroligomers of: glycolide, dl-lactide, d-lactide, l-lactide, caprolactone,dioxanone and trimethylene carbonate or their copolymers;polyhydroxyacids, polyesters, polyorthocarbonates, polyanhydrides,polylactones, polyaminoacids and polyphosphates. Biodegradable polymerssuitable for this application must have melting point between 40 to 70°C. Even more preferably, the melting point must be between 40 to 55° C.The preferred polymers or copolymers or their blends and derivativesthat can be used in this application include, but not limited to:polycaprolactone, polycaprolactone-polyethylene glycol block copolymers,polyethylene glycol-polyhydroxy acid copolymers, polyethyleneglycol-polylactone block copolymers. Polyethyleneglycol-polytrimethylene carbonate block copolymers. The polyethyleneglycol block copolymers may be AB, ABA or BAB type.

The polymer architecture such as number of branches per molecule may bealtered to achieve a suitable melting point. For example, branched orstar shaped polymers generally have lower melting points as compared totheir linear analogs. A synthesis of low melting polyethylene glycolpolylactide block copolymer is shown in one illustrative example.Polymers that generate low melt viscosity are even more preferred.

Iodinated compounds that can be used to provide a radio-opaque propertyshould be safely removed from the human or animal body. The preferrediodinated compounds are water-soluble and have 3 to 4 iodine atoms permolecule. The preferred iodine compounds include, but not limited to:iohexyl, metrizamide, iopamidol,3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid, meglumine diatrizoate,iopentol, iopromide, triiodobenzoic acid, erythrosine and ioversol. Theiodinated compound is added in sufficient amount to produce a goodquality image in medical X-ray image apparatus. The amount of iodineused may vary depending on the medical X-ray imaging technology used.The newer machines with better detectors or x-ray film may need smallamount of iodine content to form a good image. The preferred amount oforganically bound iodine in the mixture may range from 5 percent to 40percent, more preferably 10 to 20 percent.

Additional additives may be added to the compositions described above.These additives may include biocompatible plasticizers that help toreduce the melting point, a biocompatible coloring agent to improvevisibility during open surgery, an antioxidant to improve shelf life, acrystallizing agent to improve solidification rate, a biocompatiblefiller that may improve mechanical properties and the like.

In various embodiments of the invention, bioactive compounds may beadded with the radio-opaque compositions described above for localtherapeutic effect. The amount of bioactive compound in the compositionmay be dependent on local disease being addressed, solubility ofcompound in the composition and toxicology of the compound. Thebioactive compound may be added from 0.1% to 40% w/w of totalcomposition. A range of 1 to 10% is even more preferred.

In another embodiment, a bioactive compound such as rifampin is added tothe low melting polymer and iodinated compound mixture. The radio-opaquebiodegradable composition can be used to release rifampin locally.

In one exemplary approach, 4 g Polycaprolactone (molecular weight 2000g/mole) and 1.0 gram 3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acidsodium salt are dissolved/suspended in dimethyl sulfoxide. The solventis removed by vacuum drying at 50° C. for 24 hours. The mixture is thenpartially filled in 3 ml polypropylene syringe. The syringe is thenheated to 70° C. for 1 hour to melt the mixture. The liquid melt can bepushed out using the syringe plunger. The biodegradable polymer andiodinated compound of the above-mentioned example is clearly visible inX-rays.

Some low melting compositions, particularly compositions prepared frompolyethylene glycol-polylactone copolymers may absorb water uponinjection in the body. The absorption of water in the body may increasethe size of the implant. The increased size of the implant mayadvantageously help the implant to entrap itself with in the tissuecavity. The absorption of water depends on the amount of polyethyleneglycol in the copolymer and its molecular weight. Polyethylene glycolwith molecular weight 400 to 20000 g/mole is most preferred. The amountof polyethylene glycol in the copolymer may range from 10% to 98% mostpreferably 40 to 70%. Such polymers may be especially useful asbiodegradable surgical/breast biopsy markers.

In some medical applications, it is necessary to use low viscosityliquids and solutions that are radio-opaque and are capable of releasinga bioactive compound in a controlled manner. This invention alsoprovides novel methods and compositions that permit injection ofradio-opaque biodegradable polymer solution in a tissue cavity.

In various embodiments of the invention, commercially availablesynthetic biodegradable polymer is dissolved in biocompatible watermiscible solvent. The radio-opacity is achieved by dissolving abiocompatible iodinated compound along with the polymer. In addition, abioactive compound may be added to achieve a desired therapeutic effect.The solution is then injected in side body or in the tissue cavity. Uponinjection, the solvent diffuses out from the mixture, leaving behind thepolymeric implant. The radio-opaque compound entrapped in the implantprovides radio-opacity, which facilitates monitoring movement anddegradation of the composition for a local therapeutic effect.

Hydrophobic biodegradable polymers are preferred for this application.The preferred polymers that can be used include, but not limited to:polymers, copolymers or oligomers or their derivatives or blends of:glycolide, di-lactide, d-lactide, l-lactide, caprolactone, dioxanone andtrimethylene carbonate or their copolymers; polyhydroxyacids,polyorthocarbonates, polyanhydrides, polylactones, polyaminoacids andpolyphosphates. Solvents that can be used to dissolve the biodegradablepolymer include solvents that are capable of dissolving the polymer andare water soluble and biocompatible. The preferred solvents that can beused include, but not limited to: dimethyl sulfoxide,n-methylpyrrolidinone, acetone, polyethylene glycol, glycerol, oleicacid, 1,-4 butane diol, propylene glycol, ethanol, ethyl lactate, andthe like. Dimethyl sulfoxide and n-methylpyrrolidinone are preferred dueto their ability to dissolve wide variety of biodegradable polymers,iodinated compounds and bioactive compounds. The iodinated compounds arepreferably water soluble and have three to 4 iodine atoms per molecule.The preferred iodine compounds include, but not limited to: iohexyl,metrizamide, iopamidol, 3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid,meglumine diatrizoate, iopentol, iopromide, triiodobenzoic acid,erythrosine and ioversol. The iodinated compound or compounds is/areadded in sufficient amount to produce a good quality image in medicalX-ray image apparatus. The amount of iodine used may vary depending onthe medical X-ray imaging technology used. The newer machines withbetter highly sensitive detector may need small amount of iodine contentto form a good image. The preferred amount of organically bound iodinein the mixture may range from 3 percent to 40 percent, more preferablyfrom 10 to 20 percent. In addition, additives such biocompatibleviscosity modifier that help to reduce the viscosity, a biocompatiblecoloring agent to improve visibility during open surgery, an antioxidantto improve shelf life and the like may be added.

The liquids or low melting biodegradable polymers described in thisinvention may be used for localized drug delivery inside a living bodyor body cavity. The biodegradable polymer may be melted inside oroutside the body using a suitable technique such as heating, laserirradiation, sonication etc. The melted polymer is then transported tothe localized site inside the human or animal body or body cavity,preferably using MIS technique. The melted biodegradable polymer is thendeposited in an amount that is sufficient for a given application. Forexample, filling the body cavity generated by tooth extraction andfilling a fractured bone defect will require different quantities of thebiodegradable polymer. The polymer then conforms to the shape of thebody cavity and solidifies. The solidified polymer is thus molded ‘insitu’ inside the human or animal body cavity.

Biodegradable Coatings and Biodegradable Medical Devices

The biodegradable radio-opaque compositions made in accordance with thepresent invention find utility in manufacturing of fibers, films,moldings and laminates for medical and surgical applications. Thesecompositions also could be used in medical device fabrication. Thesedevices are prepared by conventional fabrication techniques. In oneembodiment, a radio-opaque terminated polymer is mixed or blended withother biodegradable polymers to produce a blend with desirableproperties. Solutions of this mixture is then either casted afterremoving the solvent or by pressing solid copolymers in hydraulic presshaving heated plates. This results in formation of films that are usedfor medical and surgical applications. Other methods of manufacturinginclude melt casting, solvent casting, pressing, compression molding,injection molding, and extrusion. Various techniques such as slowcooling, rapid cooling, quenching may be employed to obtain a desiredmorphology of processed solids. The radio-opaque polymers produced inaccording with the present invention can be modified further, by theaddition of pharmaceutically acceptable: antioxidant, plasticizer,coloring agent, filler, and the like.

The biodegradable iodinated end-capped polymers of the present inventionare also useful in the manufacturing of molded solid surgical aids. Lowmolecular weight polymers with high iodine content are used asplasticizers for commercial biodegradable polymers. Some of thecompositions described herein can be used as scaffolds for tissueengineering applications. Some of the iodinated end-capped polymersproduced in accordance with the present invention also find utility incoating biodegradable fibers, filaments or suture materials. It will beapparent to a person skilled in the art that other variations of thepresent invention may find related applications.

The biodegradable radio-opaque polymers described in this invention maybe used to make biodegradable coatings for implantable devises, asmaterial for guided tissue regeneration, for postoperative adhesionprevention, and controlled drug delivery. Examples of biodegradablemedical devices include, but are not limited to biodegradable stentsthat may be used in angioplasty or biodegradable, sutures, screws,staples, biodegradable spinal implants and cages etc. The radio-opaquecoating permits easy visualization during a surgical procedure and alsoconfirms the implant's position after surgery. Such coatings may beformed by polymeric coating methods known in the art. For example, inone embodiment, a spray drying or dip coating process may be used incoating a biodegradable medical device. In another embodiment, dipcoating may be used to coat a biodegradable stent.

In an embodiment of the invention, the polymer is used to coat Nitinolbased medical devices such as coronary or peripheral stents and stentgrafts. The coating may be carried out using spry or dip coating method.

In another embodiment of the invention iodinated compositions describedin this invention may also be physically mixed or blended to produce aradio-opaque biodegradable device. Radio-opaque compound such as Iohexylis added to polymer mixture in the range of 0.1% to 90%, more preciselyin the 5% to 30% range.

Biopsy Markers

In various embodiments of the inventions, surgical biopsy markers aremade by combination of hydrophobic and hydrophilic biodegradablepolymers. In another embodiment of the invention, water soluble polymerssuch polyethylene glycol (molecular weight 20000 g/mole) is blended withradio-opaque contrast agents and/or magnetic resonance imagingcompounds. In an embodiment of the invention, various mixtures ofpolyethylene glycol, molecular weight 20000 g/mole (PEG 20K) and sodiumdiatrizoate dehydrate (SD) were mixed and heated at 70° C. for 30minutes in a cylindrical mold. The PEG melts and acts a binder for SDparticles. The mixture is cooled, isolated and loaded in a 3 mlpolypropylene syringe. The syringe was imaged using a standard medicalx-ray imaging equipment. The quality of x-ray image is assessed as noimage or poor image, acceptable, good, and very good The amount of PEGand SD used and the quality of image obtained is summarized in Table 8.

TABLE 8 Calculated Sodium iodine Quality of diatrizoate PEG content ofX-ray (g) 20K (g) mixture (%_(—) image 0 1.0 0 No image 0.088 0.911 5Acceptable 0.177 0.824 10 Good 0.265 0.735 15 Good 0.353 0.647 20 Verygood 0.441 0.559 25 Very good 0.530 0.471 30 Very good

In another embodiment, 10 g of polyethylene glycol is mixed with 15 giohexyl (a standard radio-opaque contrast agent). The mixture is heatedto 60° C. to melt polyethylene glycol and blended to form a uniformdispersion and cooled. The mixture is filled inside a hollow tube madefrom biodegradable polymers such as copolymer of polylactones orpolyglycolide-polylactate and closed so that the contrast agent mixtureis completely covered by the biodegradable polymer. This device canserve as biodegradable surgical marker. Many changes in the size andshape of the device can be made. A spherical or cylindrical device thatcan be delivered using commercially available surgical biopsy system ispreferred. The outer skin of biodegradable polymer on the deviceprevents the dissolution of the polyethylene glycol and imaging agentfilled inside the hollow cavity. After degradation of outer skin,polyethylene glycol and imaging agent iohexyl are safely eliminated fromthe body. In some embodiments, it is preferred to have a syntheticradio-opaque polymer that is radio-opaque and is also porous in nature.The porosity is deliberately created to make the radio-opaque polymervisible in ultrasonic imaging technique. Many methods of porositypreparation known in the art used. These include but not limited to:porosity by lyophilization, porosity by entrapping a pressurized gassuch a carbon dioxide gas, porosity induced by salt leaching methods,porosity formed by foam producing compounds such as sodium bicarbonate.In one exemplary embodiment, porosity is created by lyophilizing asolution of radio-opaque polymer. In one exemplary embodiment, a 10%solution of polylactide-co-polyglycolide (50:50) in dioxane incylindrical mold along with iopamidol (25% by weight) is frozen bycooling at the solution to −20° C. The dioxane solvent is then sublimedaround 0° C. under vacuum (lyophilization) to form a porousbiodegradable polymer that has atleast 10% organically bound iodine. Thesynthetic biodegradable radio-opaque foam may be useful as surgicalbiopsy marker especially breast biopsy marker.

Many iodinated compositions described in this invention are susceptiblefor degradation when exposed to high energy electromagnetic radiationsuch as ultraviolet light, and gamma radiation. Therefore, sterilizationprocedures which use ultraviolet light and gamma radiation are leastpreferred in making medical devices and pharmaceutical compositions. Thepreferred methods of sterilization for radio-opaque compositionsdescribed in this invention include any method which does not ushigh-energy electromagnetic radiation and include but not limited to:ethylene oxide, propylene oxide, hydrogen peroxide, ozone, and iodinebased sterilization methods known in the medical device orpharmaceutical dosage preparation art. Steam or heat based sterilizationmay also be used. Ethylene oxide based sterilization method is mostpreferred.

The following non-limiting examples are intended to illustrate theinventive concepts disclosed in this document. Those skilled in the artwill appreciate that modifications can be made to these examples,drawings, illustrations and claims, which are intended to fall withinthe scope, the present invention.

Materials and Equipment

Polyethylene glycol can be purchased form various sources such asShearwater Polymers, Dow Chemicals (Union Carbide), Fluka andPolysciences. Multifunctional hydroxyl and amine terminated polyethyleneglycol are purchased from Shearwater Polymers (Nektor Therapeutics,Huntsville Al), Dow Chemicals and Texaco. Amine terminated polyethyleneglycols also can be synthesized using methods known in the prior art.Dicyclohexylcarbodiimide (Product Number: D8, 000-2),N-(3-Dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC)(Product Number: 03450) are purchased from Sigma-Aldrich. Pluronic® andTetronic® series polyols can be purchased from BASF Corporation orSigma-Aldrich. Cyclic lactones, useful for syntheis of biodegradablepolymers, such as DL-lactide, glycolide, caprolactone and trimethylenecarbonate can be obtained from commercial sources like Purac, DuPont,Polysciences, Aldrich, Fluka, Medisorb, Wako and Boehringer Ingelheim.N-hydroxysulfosuccinimide can be purchased from Pierce andSigma-Aldrich. Iodinated compounds like Metrizamide (Product Number:69753), 3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid, sodium salt(product Number: 33469) 2,3,5-Triiodobenzyl alcohol (Product Number: 52,690-8) triiodobenzoic acid can be purchased from Sigma-Aldrich.Alternatively, commercially available x-ray contrast media solutionssuch as ISOVUE™-300 solution can be purchased from local pharmacy. Thecontrast medial solutions may be lyophilized to recover the iodinatedcompound. Biodegradable polymers such as polylactide, polyglycolide,polycaprolactone and their derivatives and copolymers can be purchasedfrom Sigma-Aldrich, and Polysciences. All other reagents, solvents areof reagent grade and can be purchased from commercial sources such asPolysciences, Fluka, ICN, Aldrich and Sigma. Most of thereagents/solvents are purified/dried using standard laboratoryprocedures such as described Perrin et al. Small laboratory equipmentand medical supplies can be purchased from Fisher, VWR or Cole-Parmer.

General Analysis

Chemical analysis for the polymers synthesized include structuraldetermination using nuclear magnetic resonance (proton and carbon-13),infrared spectroscopy, high pressure liquid chromatography and gelpermeation chromatography (for molecular weight determination). Thermalcharacterization such as melting point and glass transition temperaturecan be done by differential scanning calorimetric analysis. The aqueoussolution properties such as self assembly, micelle formation, gelformation can be determined by fluorescence spectroscopy, UV-visiblespectroscopy and laser light scattering instruments. Mechanicalproperties such as tensile strength, modulus, percent elongation atbreak are determined using Instron.

In vitro degradation of the polymers is followed gravimetrically at 37°C., in aqueous buffered medium such as phosphate buffered saline (pH7.2). In vivo biocompatibility and degradation life times are assessedby injecting or forming a gelling formulation directly into theperitoneal cavity of a rat or rabbit and observing its degradation overa period of 2 days to 12 months. Alternatively, the degradation isassessed by the prefabricated sterile implant made by process like bysolution casting. The implant is then surgically implanted within theanimal body. The degradation of the implant over time is monitoredgravimetrically or by chemical analysis. The biocompatibility of theimplant can be assessed by standard histological techniques. Drugelution profiles are measured high pressure liquid chromatography.

EXAMPLE 1

Polymeric Liquid Contrast Agent

Synthesis of Polyethylene Glycol 400 Terminated with Triiodobenzoate

A 3 necked flask equipped with magnetic stirrer and nitrogen inlet ischarged with 5 g polyethylene glycol, molecular weight 400 and 50 mlDMF. The solution is cooled 0° C. using ice bath and 13.7 gtriiodobenzoic acid and 7.5 g 1,3-dicyclohexyl carbodiimide are added tothe reaction mixture. The mixture is stirred at 0° C. for 6 h and thenovernight at room temperature under nitrogen atmosphere.Dicyclohexylurea is removed by filtration and triiodobenzoate ester isby isolated by removing DMF under vacuum. A toluene solution of crudeproduct is purified by column chromatography using alumina. The finalproduct, a viscous oily liquid is stored in amber colored vial undernitrogen atmosphere at 4° C. The product shows at least 1 g/100 mlsolubility in water.

EXAMPLE 2

Synthesis of Triiodophenol Ester of Polyethylene Glycol 600 Diacid

5 g Polyethylene glycol 600 diacid is dissolved in 100 ml drydichloromethane.

The solution is cooled to 4° C. 4.9 g 1,3-dicyclohexyl carbodiimide(DCC) and 8.6 g triiodophenol are added to the reaction mixture. Themixture is stirred at 4° C. for 6 h and overnight at room temperatureunder nitrogen atmosphere. Dicyclohexylurea is removed by filtration andthe PEG ester is by isolated by removing the dichloromethane. It isfurther purified by column chromatography using alumina as a substrateand toluene as a mobile phase. The product is stored under nitrogenatmosphere at −20° C.

EXAMPLE 3

Synthesis of Polyethylene Glycol Terminated with Triiodophenol byEthoxylation of Triiodophenol

10 g triiodophenol is charged into flame dried 250 ml reaction flask.The phenol is then heated to 60° C. under vacuum for 24 h to removetraces of moisture from the phenol. 50 ml anhydrous tetrahydrofuran(THF) is added under nitrogen atmosphere. After complete dissolution ofthe polymer in THF, 3.5 g of potassium naphthalide is added undernitrogen atmosphere. The reaction flask is then cooled to 0° C. usingice-bath and 22 g of ethylene oxide is added using a cold syringe. Thereaction is continued at 0° C. for 72 h under nitrogen atmosphere. Atthe end of 72 h period, 1 ml water is added to the THF solution and themixture is stirred for another 1 h. It is then added to 4000 ml coldhexane to precipitate the polymer. The polymer is purified by severalprecipitations from toluene-hexane solvent non-solvent system and driedunder vacuum at 60° C. for 24 our. Using a similar procedure, ethyleneoxide polymerization may be initiated using hydroxy groups and primaryand secondary amine hydrogen atoms on Iohexyl, Metrizamide, iopamidol,iopentol, iopromide, and Ioversol. The molar ratio of ethylene oxide toinitiating group will determine the degree of polymerization ofpolyethylene glycol chain.

EXAMPLE 4

Synthesis of three arm polyethylene glycol terminated withtriiodobenzoate

A 250 ml 3 necked flask equipped with magnetic stirrer and nitrogeninlet is charged with 5 g polyethylene glycol (molecular weight 1000Daltons, 3 arms, 3 terminal hydroxyl groups per molecule) and 130 mlbenzene. 20 ml benzene is distilled out to remove traces of moisturefrom the solution. The solution is then cooled 4° C. and 12.5 gtriiodobenzoic acid and 6.7 g of 1,3-dicyclohexyl carbodiimide are addedto the reaction mixture. The mixture is stirred at 4° C. for 6 h andovernight at room temperature under nitrogen atmosphere.Dicyclohexylurea is removed by filtration and triiodo derivative isisolated by removing the benzene under vacuum and repeated precipitationusing toluene-hexane solvent-nonsolvent system. The viscous liquid oilyproduct is stored under nitrogen atmosphere at 4° C. until further use.

EXAMPLE 5

Synthesis of Polyethylene Glycol Terminated with Erythrosin

A solution of Erythrosin (acid form, 9.7 g),N,N′-dicyclohexylcarbodiimide (2.93 g), polyethylene glycol (molecularweight 1000 Daltons, 5.0 g) and dimethylaminopyridine (0.148 g) in 100ml dry DMF is stirred at 0° C. for 16 h under nitrogen atmosphere. Thereaction mixture is then filtered to remove urea. The solvent is removedfrom the filtrate using vacuum distillation to yield a crude product.The crude product is then dissolved in 10 ml toluene and added to 1000ml ice-cold hexane. The precipitated PEG having terminal Erythrosingroup is isolated and dried overnight under vacuum at 60 0° C. UV-VISspectrum of PEG endcapped product shows absorption in VIS region.

EXAMPLE 6

Synthesis Polyethylene Glycol Triiodobenzoate

5 g polyethylene glycol, molecular weight 1000, is dissolved in 100 mldry DMF. The solution is cooled to 4° C. and 2.9 g of 1,3-dicyclohexylcarbodiimide (DCC) and 5.5 g triiodobenzoic acid are added to thereaction mixture. The mixture is stirred at 4° C. for 6 h and overnightat room temperature under nitrogen atmosphere. Dicyclohexylurea isremoved by filtration and the triiodo derivative is by isolated byremoving the DMF under vacuum and repeated precipitation usingtoluene-hexane solvent-nonsolvent system. The product is stored undernitrogen atmosphere at −20° C.

EXAMPLE 7

Synthesis of Polyethyleneglycol Triiodobenzamde Using Amine TerminatedPolyether (Jefffamine®)

10 g Jefffamine® (Jefffamine® ED-2003 or Huntsman XTJ-502, averagemolecular weight 1900) is dissolved in 200 ml dry DMF. The solution iscooled to 4° C. 2.9 g of 1,3-dicyclohexyl carbodiimide (DCC) and 5.5 gtriiodobenzoic acid are added to the reaction mixture. The mixture isstirred at 4° C. for 6 h and overnight at room temperature undernitrogen atmosphere. Dicyclohexylurea is removed by filtration andPEG-triiodobenzamde by isolated by removing the DMF under vacuum andrepeated precipitation using toluene-hexane solvent-nonsolvent system.The product is stored under nitrogen atmosphere at −20 C.

EXAMPLE 8

Synthesis of 8 Arm Polyethylene Glycol Terminated with Triiodobenzamde

10 g 8 arm amine terminated polyethylene glycol, molecular weight 20000(Shearwater, custom synthesized from 8 arm 20000 polyethylene glycol) isdissolved in 200 ml dry toluene. 20 ml toluene is removed bydistillation and then the solution is cooled to 4° C. 1.1 g1,3-dicyclohexyl carbodiimide (DCC) and 2.0 g triiodobenzoic acids areadded to the reaction mixture. The mixture is stirred at 4° C. for 6 hand overnight at room temperature under nitrogen atmosphere.Dicyclohexylurea is removed by filtration and PEG-triiodobenzamde byisolated by precipitating in ether. It is then purified by repeatedprecipitation using toluene-hexane solvent-nonsolvent system. Theproduct is stored under nitrogen atmosphere at −20 C until further use.

EXAMPLE 9

Synthesis of PEO-PPO-PEO Block Copolymer Terminated with Triiodobenzoate

Synthesis of Thermosensitive Radio-Opaque Polymer

20 g PEO-PEO-PEO block copolymer, molecular weight 8000, PEOcontent >70% (Pluronic F68 obtained from BASF corporation) is dissolvedin 200 ml dry toluene. 20 ml toluene is removed by distillation and thenthe solution is cooled to 4° C. 1.5 g 1,3-dicyclohexyl carbodiimide(DCC) and 2.4 g triiodobenzoic acids are added to the reaction mixture.The mixture is stirred at 4° C. for 6 h and overnight at roomtemperature under nitrogen atmosphere. Dicyclohexylurea is removed byfiltration and PEG-triiodobenzamde by isolated by adding the filtrate in5000 ml ether. It is then purified by repeated precipitation usingtoluene-hexane solvent-nonsolvent system

A 30% solution of this polymer in saline shows thermoreversiblegelation. When the solution is cooled to 4 degree C., it forms a clearliquid. Upon warming to 37 degree C., the solution forms viscous gel.Upon cooling, the gel forms solution again (thermoreversible gelation).The solution as well as gel show better contrast in x-ray imaging whencompared to the unmodified polymer. Thus the polymer solution displaysbetter visibility under x-ray imaging as well as thermoreversiblegelation property.

The thermoreversible described above gelation may be carried out ‘insitu’ on the tissue or inside a body cavity during a surgical procedure.A hydrophobic bioactive compound such as paclitaxel may be dissolved insolution or gel and released in a controlled manner.

EXAMPLE 10

Aqueous Compositions for Medical X-Ray Imaging (as a Contrast Agent)

In a 100 ml volumetric flask, 30 ml distilled water, 40 g Jefffamine®triiodobenzamde (Example 7), 0.15 g triethanol amine, 0.19 g triethanolamine hydrochloride, and 0.36 g sodium chloride are added and themixture is shaken till all components are dissolved. The final volume ofthe solution is adjusted to 100 ml using distilled deionized water. Thesolution is filter sterilized using 0.2 micron filter. Alternately, thesolution can be steam sterilized.

EXAMPLE 11

Aqueous Compositions Comprising Polymeric and Non-Polymeric Non-IonicContrast Agents

In a 100 ml volumetric flask, 29 ml triethanol amine buffer (pH 7.2), 28g PEG 2000 triiodobenzamde (Example 7) and 43 g Iohexyl(5-[N-(2,3-Dihydroxypropyl)acetamido]-2,4,6-triiodo-N,N-bis(2,3-dihydroxypropyl)isophthalamide)are mixed. The final volume is adjusted to 100 ml using triethanol aminebuffer solution. The solution is filter sterilized.

EXAMPLE 12

Aqueous Compositions for X-Ray Imaging Comprising Antioxidant, DefoamingAgent, and Viscosity Reducing Agent

In a 100 ml volumetric flask, 30 ml distilled water, 40 g Jefffamine®triiodobenzamde 0.15 g triethanol amine, 0.19 g triethanol aminehydrochloride, 0.36 g sodium chloride and 0.005 g BHT dissolved in 8 mlethanol are added. The mixture is shaken till all components aredissolved. 0.2 g 1-octanol is added to the mixture and the final volumeof the solution is adjusted to 100 ml using distilled deionized water.The solution is filter sterilized using 0.2 micron filter.

EXAMPLE 13

Polymeric Neat Liquids as Contrast Agent

20 g anhydrous ethanol and 80 g PEG 1000 triiodobenzoate are mixed in250 ml volumetric flask. The solution is warmed to 50° C. for 1 h toform a homogeneous solution. The solution is filtered using 0.2 micronfilter and stored until use.

EXAMPLE 14

Contrast Agent Formulation in Water Miscible Organic Solvents

10 g anhydrous ethanol, 10 g n-methylpyrrolidinone and 80 g PEG 1000triiodobenzoate are mixed in a 250 ml volumetric flask. The solution iswarmed to 50° C. for 1 h to form a homogeneous solution. The solution isfiltered using 0.2 micron filter and stored until use.

EXAMPLE 15

Contrast Agent Formulation where Polymer Shows Self Assembly of IodineMoieties in Aqueous Solution

In a 100 ml volumetric flask, 40 ml triethanol amine buffer (pH 7.2), 25g PEG 20000 triiodobenzamde with 8 arms (example 8) and are mixed. Thefinal volume is adjusted to 100 ml using triethanol amine buffersolution. The solution is filter sterilized using 200 micron filter.

EXAMPLE 16

Radio-Opaque Biodegradable Crosslinkable Polymer Composition

a) Synthesis of Crosslinkable Hydrophobic Synthetic BiodegradablePolymer

Part 1: Preparation of trifunctional caprolactone-lactate liquidcopolymer Trimethylol propane triol (TMPT) is dried under vacuum at 60°C. for 16 hours. 2 g of dry TMPT, 17.5 g of dl-lactide, and 20 mg ofstannous octoate are charged into a 3 necked flask equipped with Tefloncoated magnetic stirring needle and nitrogen inlet. The flask is thenimmersed into silicone oil bath maintained at 160° C. The reaction iscarried out for 5 h under nitrogen atmosphere. The reaction mixture isthen cooled to room temperature. The mixture is then dissolved in 10 mltoluene. The hydroxy terminated liquid lactate polymer is isolated bypouring the toluene solution in large excess cold hexane. It is furtherpurified by repeated dissolution-precipitation process fromtoluene-hexane solvent-nonsolvent system and dried under vacuum at 60°C. It is then immediately used for acrylate end capping reactionmentioned below:

Part 2: End Capping of Trifunctional Polylactide Polymer with AcrylateGroup

10 g of TMPT initiated lactate synthesized previously is dissolved in150 ml dry benzene and 2.7 ml of triethyl amine. 20 ml benzene isdistilled out. The solution is cooled to 0° C. in ice bath. 1.8 mlacryloyl chloride is added dropwise to the cold lactate solution. Themixture is refluxed under nitrogen atmosphere for 3 h. The solution isfiltered to remove triethylamine hydrochloride. The acrylate ester isthen isolated by pouring the filtered solution in large excess coldhexane. It is further purified by repeated (3 times) precipitation fromtoluene-cold hexane system. The liquid polymer is dried under vacuum at40° C. It is stored in amber colored bottle under nitrogen atmosphere.

b) Radio-Opaque Crosslinkable Biodegradable Polymer

The liquid crosslinkable polymer is made radio-opaque bydispersing/dissolving commercially available contrast agents such asIohexyl prior to crosslinking. Thus, 2 grams of polymer is mixed with 1g of Iohexyl and 0.010 g benzoyl peroxide. The mixture is heated to 60degree C. until gelation and crosslinking. The crosslinked polymerundergoes degradation upon implantation while Iohexyl in the polymerprovides visibility in x-ray imaging. Iohexyl may be added in 0.1% to89% weight range. The preferred range is between 5 to 30%. The liquidacrylate polymer can be free radically polymerized ‘in situ’ inside thehuman body. The preferred way is visible light initiatedphotopolymerization. The crosslinking may be performed outside prior toimplantation. The radio-opaque polymer may be of used to makeradio-opaque microspheres.

EXAMPLE 17

Synthesis of Low Temperature Melting (<60° C.) Radio-Opaque InjectablePolymeric Composition

2.00 g polyethylene glycol 2000, 7.2 g of dl-lactide, 5.7 g caprolactoneand 30 mg of stannous octoate are charged into 100 ml Pyrex pressuresealing tube. The tube is frozen in liquid nitrogen and connected tovacuum line for 10 minutes. The tube is then connected to argon gas lineand sealed under argon. The sealed tube is immersed in oil bathmaintained at 140° C. The polymerization is carried out for 16 h at 140°C. The polymer from the tube is recovered by breaking the Pyrex tube.The polymer is then dissolved in 20 ml chloroform and precipitated in2000 ml hexane. The precipitated polymer is recovered by filtration anddried under vacuum for 1 day at 60° C.

The injectable polymer synthesized above is mixed with iodinatedcompounds such as Iohexyl prior to injecting into human body. TheIohexyl biodegradable polymer mixture is melted “in situ” at allocalized site inside the body during a surgical procedure. The presenceof Iohexyl makes the polymer radio-opaque. The amount of iohexyl in thepolymer may range from 5% to 60%. The iodine content of finalcomposition may range from 5 to 30% more preferably 10-20%.

EXAMPLE 18

Coating of Biodegradable Stent Using Biodegradable Coating ComprisingIodinated Compounds or Biodegradable Radio-Opaque Ink

1 g Polylactide-co-polyglycolide (50:50) copolymer (average molecularweight 25000-50000) is dissolved in 100 ml dimethyl sulfoxide. To thissolution 400 mg Iohexyl (exemplary water soluble, non-ionic radio-opaquecompound) is added. The solution/suspension is used in coating variousbiodegradable polymeric devices. The solution could also be used as abiodegradable radio-opaque ink. The coating solution may be added withbioactive compounds such as Paclitaxel or Rapamycin to reducerestenosis.

Coating of Biodegradable Stents Using Biodegradable Radio-Opaque CoatingComposition

A balloon expandable biodegradable stent fabricated using syntheticbiodegradable polymers such as polyhydroxy acids or polylactones isexpanded and dip coated or spray coated using coating solution mentionedabove. The coated stent is dried in air and finally in vacuum at 60° C.for 24 h. The coated stent is compressed and mounted on angioplastyballoon and stent catheter delivery system. The stent and its deliverysystem is sterilized using ethylene oxide. The stent is then deployedusing balloon angioplasty technique and expanded in situ at the site ofblockage. The biodegradable stent is visible during deployment due tobiodegradable radio-opaque coating. Alternatively suspension of silversalts such as silver chloride, silver acetate, and silver lactate may beused in place of iodinated compound. The coating thickness on stent mayrange from 2 micron to 2000 microns, more preferably 10 to 50 microns.The iodine content of coating may range from 5 to 40%, preferably 10 to30% to provide sufficient visibility of stent during deployment.

EXAMPLE 19

X-ray visible injectable controlled release drug composition

2.00 g polyethylene glycol 2000, 7.2 g of dl-lactide, 5.7 g caprolactoneand 30 mg of stannous octoate are charged into 100 ml Pyrex PressureSealing Tube. The Tube is frozen in liquid nitrogen and connected tovacuum line for 10 minutes. The tube is then connected to argon gas lineand sealed under argon. The sealed tube is immersed in oil bathmaintained at 140° C. The polymerization is carried out for 16 h at 140°C. The polymer from the tube is recovered by breaking the Pyrex tube.The polymer is then dissolved in 20 ml chloroform and precipitated in2000 ml hexane. The precipitated polymer is recovered by filtration anddried under vacuum for 1 day at 60° C.

3.5 g of polymer synthesized as above is mixed with 0.5 g of rifampin,1.5 g of Iopamidol and 25 ml tetrahydrofuran and 25 ml dimethylsulfoxide. The mixture is warmed to 40 to prepare a homogeneous mixture.It is filtered through 0.2 micron filter. The solvents are removed undervacuum. The polymer mixture is sterilized by ethylene oxide and injectedinto a dental cavity created by removal of tooth. The polymer mixture isvisible when viewed using medical x-ray imaging techniques. A rifampinrelease from the mixture demonstrates a release of bioactive compound.

EXAMPLE 20

In Situ Melting of Injectable Formulation Comprising Iodinated Compound

3 g Polycaprolactone (molecular weight 2000) and 0.25 g rifampin and 1.0g 3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid are dissolved/suspendedin 10 ml dimethyl sulfoxide. Solvent is removed air drying in chemicalhood and finally under vacuum at 60° C. for 24 hours. The mixture isfilled in a special syringe which can be heated to 60° C. and issterilized using ethylene oxide. The polymer composition is heated to55° C. and melted. The melting is done just prior to implantation or insitu in side the body. This melted mixture is used in the surgicalprocedure where it is used to fill a body cavity.

EXAMPLE 21

Solvent Based Radio-Opaque Biodegradable Injectable Composition

Biodegradable polymer and iodinated organic compound dissolved in watermiscible organic solvent and injected in situ during a surgicalprocedure

1 g Polylactide, molecular weight 2000 (PLA), 0.2 g Iohexyl aredissolved/dispersed in 10 ml n-methylpyrolidonone (NMP). The mixture istransferred into a 20 ml sterile syringe. The mixture is used in coatingan organ or filling a tissue cavity. The NMP is miscible with tissuefluids and washes away leaving behind a PLA and Iohexyl. The implantedPLA with Iohexyl can be viewed using medical x-ray imaging techniques.In place of Iohexyl, other radio-opaque agents such as Metrizamide,iopamidol, iopentol, iopromide, and Ioversol may also be used. Silversalts may also be used to make the biodegradable polymer radio-opaque.The percentage of radio-opaque compound such as Iohexyl in the polymermay be varied; it may be ranged between 0.1% to 90%, more preferablyfrom 5% to 40%.

EXAMPLE 22

Synthesis of Rose Bengal Terminated Polyethylene Glycol

2 g of PEG 1000 (molecular weight 1000 Daltons) is dissolved in 100 mldry benzene. About 50 ml of benzene is distilled out to remove traces ofwater from the PEG solution. The warm solution is cooled to roomtemperature and, 50 ml dry acetone and 4.068 g of Rose Bengal (free acidform) and 1 drop of sulfuric acid are added. The reaction mixture isrefluxed for 4 h. The solution is then cooled and filtered. The filtrateis added to 2000 ml cold hexane. The precipitated Rose Bengal terminatedpolymer is dried at 60° C. under vacuum for 24 h.

EXAMPLE 23

Visibility of Peg End Capped with Iodine Containing Compounds UsingMedical X-Ray Imaging Technique

1 ml of neat liquid polymer with triiodobenzoate group synthesizedaccording to earlier example is placed into 1 ml graduated pipette. Thetube is sealed on both sides using adhesive tape. This glass pipette isglued onto a sheet of paper and a 15 mm thick Plexi glass sheet is kepton top of tube (to simulate the x-ray absorption by the human chest) andX-ray photographs of the pipette are taken using a fluoroscope (made bySiemens). The x-ray absorption due to PEG triiodo liquid ester isclearly seen in the developed x-ray film.

EXAMPLE 24

Coating of biodegradable devices using biodegradable coating comprisingiodinated compounds. Coating using blends of two biodegradable polymers

3 g Polylactide-co-polyglycolide (50:50) copolymer (average molecularweight 25000-50000) is dissolved in 100 ml chloroform. To this solution0.1 g polylactic acid or polycaprolactone, molecular weight 1000,endcapped with triiodobenzoic acid is added (see examples 25 forsynthesis). The solution is used in coating various biodegradablepolymeric devices.

Coating of Vicryl Suture:

The Iohexyl solution prepared above is loaded into standard sprypainting apparatus. The solution is spray coated on 4-0 Vicryl sutures(Ethicon Inc). The coated sutures are dried on vacuum at 60° C. for 24h. The coated suture is sterilized using ethylene oxide. The coatedsterile suture is used in joining soft tissue in an animal surgery. Thecoated suture is visible when viewed using standard medical x-rayapparatus. The suture may also be dip coated. If needed, iodinatedcompounds such as Iohexyl may be added in coating formulation toincrease iodine content and therefore image quality of the coating.

EXAMPLE 25

Preparation of Oligo Polylactic Acid End-Capped with Two Iodinated EndGroups

Part 1: Synthesis of Polylactic Acid

2.00 g of diethylene glycol, 16.28 g of dl-lactide and 30 mg of stannousoctoate are charged into 100 ml Pyrex pressure sealing tube. The tube isfrozen in liquid nitrogen and connected to vacuum line for 10 minutes.The tube is then connected to argon gas line and sealed under argon. Thetube is then immersed in oil bath maintained at 140° C. Thepolymerization is carried out for 16 h at 140° C. The polymer from thetube is recovered by breaking the Pyrex tube. The polymer is thendissolved in 30 ml chloroform and precipitated in cold 2000 ml hexane.The precipitated polymer is recovered by filtration and dried undervacuum for 1 day at 60° C. It then immediately used in end-cappingreaction.

Part 2: End-Capping of Polylactic Acid with Triiodobenzoyl Chloride

5 g of PLA (synthesized previously) is dissolved in 150 ml dry toluene.About 50 ml of toluene is distilled to remove traces of water from thereaction mixture. The warm solution is cooled to 30° C. To this warmsolution, 1.3 ml of triethyl amine and 5.9 g of triiodobenzoyl chlorideare added. The reaction mixture is then refluxed for 2 h and filtered.The product is precipitated by adding the filtrate to 2000 ml cold dryhexane and filtration. It is then dried under vacuum for 12 h at 50° C.

EXAMPLE 26

Preparation of 5 Arm Polycaprolactone Terminated with TriiodobenzoicAcid

Part 1: Preparation of Xylitol Initiated Polycaprolactone

2 g of xylitol, 22.5 g of caprolactone and 30 mg of stannous octoate arecharged in a 100 ml glass sealing tube. The tube is then sealed underargon atmosphere. The sealed tube is then heated in silicone oil bathmaintained at 160° C. The contents of the tube are manually shaken forevery 10 minutes. The reaction continued for 18 hours. At the end of thereaction, the tube is cooled to room temperature and the xylitolcaprolactone is isolated by breaking the glass tube. The polymer isfurther purified by precipitation from toluene-hexane solvent-nonsolventsystem. It is dried overnight under vacuum at 60° C.

Part 2a: End Capping of Xylitol Polycaprolactone with TriiodobenzoicAcid

10 g of xylitol caprolactone is dissolved in 300 ml dry toluene. About30 ml of toluene is distilled off from the solution to remove the tracesof moisture absorbed during the previous synthesis workup. The mixtureis cooled to 0-30° C. and 14.8 g triiodobenzoic acid and 7.9 g1,3-dicyclohexyl carbodiimide are added to the reaction mixture. Themixture is stirred at 4° C. for 6 h and overnight at room temperatureunder nitrogen atmosphere. Dicyclohexylurea is removed by filtration andtriiodo derivative is isolated by removing the benzene under vacuum andrepeated precipitation using toluene-hexane solvent-nonsolvent system.The viscous liquid oily product is stored under nitrogen atmosphere, inamber color vial, at 4 C until further use.

Part 2b: End Capping of Xylitol Polycaprolactone with3,5-Bis(Acetylamino)-2,4,6-Triiodobenzoic Acid

10 g of xylitol caprolactone is dissolved in 300 ml drydimethylfroamamide. About 30 ml of toluene is distilled off from thesolution to remove the traces of moisture absorbed during the previoussynthesis workup. The mixture is cooled to 0-30° C. and 19.2 g3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid and 7.9 g1,3-dicyclohexyl carbodiimide are added to the reaction mixture. Themixture is stirred at 4° C. for 6 h and overnight at room temperatureunder nitrogen atmosphere. Dicyclohexylurea is removed by filtration andtriiodo derivative is isolated by removing the dimethylformamdie undervacuum and repeated precipitation using toluene-hexanesolvent-nonsolvent system. The viscous liquid oily product is storedunder nitrogen atmosphere, in amber color vial, at 4 C until furtheruse.

EXAMPLE 27

Oligomeric Polyhydroxy Polymer Terminated with Erythrosin

Part 1: Preparation of Trifunctional Lactate Liquid Copolymer

Trimethylol propane triol (TMPT) is dried at 60° C. overnight undervacuum prior to use. 2 g of dry TMPT, 17.5 g of dl-lactide, and 20 mg ofstannous octoate are charged into a 3 necked flask equipped with Tefloncoated magnetic stirring needle and nitrogen inlet. The flask is thenimmersed into silicone oil bath maintained at 160° C. The reaction iscarried out for 5 h under nitrogen atmosphere. The reaction mixture isthen cooled to room temperature. The mixture is then dissolved in 100 mltoluene. The hydroxy terminated liquid lactate polymer is isolated bypouring the toluene solution in large excess cold hexane. It is furtherpurified by repeated dissolution-precipitation process fromtoluene-hexane solvent-nonsolvent system and dried under vacuum at 60°C. It is then immediately used for end-capping reaction mentioned below:

Part 2a: End Capping of Trifunctional Polymer with Erythrosin

5 g of TMPT initiated lactate is dissolved in 100 ml dry benzene and 9.1g Erythrosin. The solution is cooled to 0° C. in ice bath. 5.2 g of DCCis added to the cold lactate solution. The mixture is stirred undernitrogen atmosphere for 3 days. The solution is filtered to remove ureaand the ester is then isolated by pouring the filtered solution in largeexcess cold hexane. It is further purified by repeated (3 times)precipitation from toluene-cold hexane system. The polymer is driedunder vacuum at 40° C. It is stored in amber colored bottle undernitrogen atmosphere at ° C.

Part 2b: End Capping of Trifunctional Polymer with3,5-Bis(Acetylamino)-2,4,6-Triiodobenzoic Acid

5 g of TMPT initiated lactate is dissolved in 100 ml dry benzene and 6.8g 3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid. The solution is cooledto 0° C. in ice bath. 5.2 g of DCC is added to the cold lactatesolution. The mixture is stirred under nitrogen atmosphere for 3 days.The solution is filtered to remove urea and the ester is then isolatedby pouring the filtered solution in large excess cold hexane. It isfurther purified by repeated (3 times) precipitation from toluene-coldhexane system. The polymer is dried under vacuum at 40° C. It is storedin amber colored bottle under nitrogen atmosphere at ° C.

EXAMPLE 28

Preparation of Blend of Synthetic Biodegradable Polymer and PolyhydroxyPolymers with Iodinated Terminal Groups

1 g polylactide-co-polylactide copolymer (50:50), 1 g iodinated groupterminated polylactic acid synthesized previously and 100 mltetrahydrofuran are dissolved in 500 ml beaker. 80 ml solvent isdistilled under vacuum and the concentrated polymer solution isprecipitated in 2000 ml cold hexane. The precipitated blend is recoveredand dried in vacuum at 30° C. for 24 until constant weight and stored at° C. under nitrogen atmosphere until further use. The blend can be usedin fabrication of various biodegradable medical devices.

EXAMPLE 29

a) Polycaprolactone Diol Terminated with Triiodobenzene

10 g polycaprolactone diol (average molecular weight 1250 purchased fromSigma-Aldrich, USA) is dissolved in 200 ml dry toluene. About 30 ml oftoluene is distilled off from the solution to remove the traces ofmoisture absorbed during the previous synthesis workup. The mixture iscooled to 0° C. and 8.8 g triiodobenzoic acid and 4.7 g 1,3-dicyclohexylcarbodiimide are added to the reaction mixture. The mixture is stirredat 4° C. for 6 h and overnight at room temperature under nitrogenatmosphere. Dicyclohexylurea is removed by filtration and triiododerivative is isolated by removing the benzene under vacuum and repeatedprecipitation using toluene-hexane solvent-nonsolvent system. Theviscous liquid oily product, is stored under nitrogen atmosphere, inamber color vial, at 4 C until further use.

b) Polycaprolactone Diol Terminated with3,5-Bis(Acetylamino)-2,4,6-Triiodobenzoic Acid

10 g polycaprolactone diol (average molecular weight 1250, purchasedfrom Sigma-Aldrich) is dissolved in 200 ml dry dimethylforamide. About30 ml of dimethylforamide is distilled off from the solution to removethe traces of moisture absorbed during the previous synthesis workup.The mixture is cooled to 0° C. and 11.4 g3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid and 4.7 g1,3-dicyclohexyl carbodiimide are added to the reaction mixture. Themixture is stirred at 4° C. for 6 h and overnight at room temperatureunder nitrogen atmosphere. Dicyclohexylurea is removed by filtration andtriiodo derivative is isolated by removing the benzene under vacuum andrepeated precipitation using toluene-hexane solvent-nonsolvent system.The viscous liquid oily product, is stored under nitrogen atmosphere, inamber color vial, at 4° C. until further use.

EXAMPLE 30

Synthesis of Polylactide with Triiodobenzoic Acid as End-Group

Polymerization of caprolactone and glycolide initiated by an iodinatedcompound.

Triiodobenzyl alcohol is dried at 60° C. overnight under vacuum prior touse. 1 g dry Triiodonenzyl alcohol 1.4 g glycolide and 1.5 gcaprolactone, and 20 mg of stannous octoate are charged into a 3 neckedflask equipped with Teflon coated magnetic stirring needle and nitrogeninlet. The flask is then immersed into silicone oil bath maintained at160° C. The reaction is carried out for 5 h under nitrogen atmosphere.The reaction mixture is then cooled to room temperature. The mixture isthen dissolved in 100 ml toluene. The iodine terminatedglycolate-caprolactone polymer is isolated by pouring the toluenesolution in large excess cold hexane. It is further purified by repeateddissolution-precipitation process from toluene-hexane solvent-nonsolventsystem and dried under vacuum at 60° C. Using a similar procedure otherhydroxy containing compounds such as Iohexyl can also be used toinitiate polymerization of lactones or cyclic carbonates.

EXAMPLE 31

Preparation of Polyethylene Glycol-Polyhydroxy Copolymer Terminated withRadio-Opaque End-Groups

Part 1: Synthesis of polyethylene glycol-co-polyglycolate copolymer(PEG2KG):

20 grams monomethoxy polyethylene glycol, molecular weight 2000 (PEG2K)is dried at 100° C. for 16 hours prior to use. 20 grams PEGM2K, 5.8 g ofglycolide and 25 mg of stannous 2-ethylhexanoate are charged into a 3necked flask equipped with a Teflon coated magnetic stirring needle. Theflask is then immersed into silicone oil bath maintained at 160° C. Thepolymerization reaction is carried out for 16 h under nitrogenatmosphere. At the end of the reaction, the reaction mixture isdissolved in 100 ml toluene. The hydroxy terminated glycolate copolymeris isolated by pouring the toluene solution in 4000 ml cold hexane. Itis further purified by repeated dissolution-precipitation process fromtoluene-hexane solvent-nonsolvent system and dried under vacuum at ° C.It is then immediately used for end capping reaction mentioned below:

Part 2: Esterification of Hydroxyl Groups with Triiodobenzoic Acid.

To a solution of 30 g of PEG2KG in 300 ml dry methylene chloride, 3.5 gtriiodobenzoic acid and 1.9 g DCC are added. The reaction mixture isstirred overnight under nitrogen atmosphere. Dicyclohexylurea is removedby filtration. The filtrate is evaporated and the residue obtained isredissolved in 100 ml toluene. The toluene solution is precipitated in2000 ml hexane. The triiodoester terminated polymer is stored undernitrogen atmosphere until further use.

EXAMPLE 32

Drug Delivery Composition Comprising Non-Polymeric Liquid, an X-RayContrast Agent and Bioactive Compound

5 g sucrose acetate (a non-polymeric controlled release medium) and 0.25g rifampin (bioactive compound) and 0.5 g Iohexyl (x-ray absorbingcompound) are dissolved/dispersed in 10 m chloroform. Most of thesolvent is removed by air drying in chemical hood. Rest of the solventis removed under vacuum at 60° C. for 24 hours. The mixture is filled ina 20 ml sterile syringe and the entire unit is sterilized by ethyleneoxide. This mixture is used in the surgical procedure where it is usedto fill a body cavity. Rifampin is released at the site of injection.The Iohexyl trapped inside the sucrose acetate improved contrast whenviewed using medical x-ray imaging systems. In place of Iohexyl, otherradio-opaque agents such as Metrizamide, iopamidol, iopentol, iopromide,and Ioversol may also be used. The percentage of radio-opaque compoundsuch as Iohexyl in the biocompatible liquid carrier may be varied, itmay be ranged between 0.1% to 90%, more preferably from 5% to 30%.

EXAMPLE 33

Synthesis of Water Soluble Activated Triiodobenzoic Acid

Synthesis of n-Hydroxysulfosuccinimide (SNHS) Derivative ofTriiodobenzoic Acid

A 3 necked flask equipped with magnetic stirrer and nitrogen inlet ischarged with 5 g of triiodobenzoic acid and 20 ml DMF. The solution iscooled 4° C. and 2.4 g of N-hydroxysulfosuccinimide and 2.9 g of1,3-dicyclohexyl carbodiimide are added to the reaction mixture. Themixture is stirred at 4° C. for 6 h and overnight at room temperatureunder nitrogen atmosphere. Dicyclohexylurea is removed by filtration andSNHS derivative is by isolated by removing the DMF under vacuum. Thecompound was further purified by column chromatography

EXAMPLE 34

a) N-hydroxysuccinimide ester of triiodobenzoic acid or3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid

1.2 g n-hydroxy succinimide and 1.1 g of triethyl amine are dissolved in100 ml benzene. The solution is cooled to 0° C. in ice bath. 1.2 gtriiodobenzoyl chloride is added dropwise to the cold alcohol solution.The mixture is then refluxed under nitrogen atmosphere for 3 h. Thesolution is filtered to remove triethylamine hydrochloride. The ester isthen isolated by removing the solvent. It is further by columnchromatography. Using a similar procedure, NHS ester of3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid can be synthesized from3,5-Bis(acetylamino)-2,4,6-triiodobenzoyl chloride

b) N-hydroxysuccinimide ester of3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid

A 3 necked flask equipped with magnetic stirrer and nitrogen inlet ischarged with 5 g 3,5-Bis(acetylamino)-2,4,6-triiodobenzoic acid and 50ml DMF. The solution is cooled 4° C. and 0.12 g ofN-hydroxysulfosuccinimide and 2.0 g of 1,3-dicyclohexyl carbodiimide areadded to the reaction mixture. The mixture is stirred at 4° C. for 6 hand overnight at room temperature under nitrogen atmosphere.Dicyclohexylurea is removed by filtration and n-hydroxysulfosuccimidederivative is isolated by removing the DMF under vacuum. The compound isfurther purified by column chromatography.

EXAMPLE 35

Synthesis of N-Hydroxysulfosuccinimide Derivative of Erythrosin

A 3 necked flask equipped with magnetic stirrer and nitrogen inlet ischarged with 5 g Erythrosin B, acid form and 50 ml DMF. The solution iscooled 4° C. and 0.71 g of N-hydroxysuccinimide and 1.67 g of1,3-dicyclohexyl carbodiimide are added to the reaction mixture. Themixture is stirred at 4° C. for 6 h and overnight at room temperatureunder nitrogen atmosphere. Dicyclohexylurea is removed by filtration andn-hydroxysuccimide derivative is isolated by removing the DMF undervacuum. The compound is further purified by column chromatography

EXAMPLE 36

Evaluation of PEG 8-Arm Polymer Terminated with Triiodobenzamde forBlood Pool Imaging

30% solution of PEG 20000, 8-arm polymer terminated with triiodobenzamdein PBS is used in the blood pooling application. This solution isinjected into white New Zealand rabbits at a dose of 3 ml/kg as a slowbolus injection. At 0.25 h, 0.5 h, 1 h and 2 h post-injection timeinterval, the opacification of the spleen liver, and blood pool asmeasured in the aorta and within the left ventricle is determined bycomputed tomography (CT) using a Toshiba 900S Imager CT scanner andassociated software. The imaging analysis is expected to show that thePEG 8-arm polymer terminated with triiodobenzamde has excellent bloodpool, liver and spleen opacification properties. Imaging at 72 hourspost injection is expected to should show complete clearance from theblood with partial clearance from the liver and spleen.

EXAMPLE 37

Proteins Chemically Modified Using Triiodobenzoic Acid Derivatives

Human monoclonal antibody modified using hydroxysuccimide ester oftriiodobenzoic acid.

100 mg of human monoclonal antibody was dissolved in 2 ml sodium boratebuffer pH 9. To this solution, 100 mg triiodobenzoic acidn-hydroxysuccimide ester, dissolved in 0.5 ml dimethyl sulfoxide isadded (example 34). The reaction mixture is shaken for 10 minutes andthe reaction is continued for 12 hours at room temperature. The reactionmixture is then dialyzed with1000 ml distilled water using 10000molecular weight cutoff dialysis membrane. The reaction mixture isfreeze dried to recover the modified antibody. The triiodobenzoic acidsubstituted antibody is used as a tissue specific x-ray contrast medium.

Using a similar procedure, amine groups of albumin or collagen can bemodified with iodinated compounds such as erythrosin or triiodobenzoicacid. The percent of amine group modification will depend on thereaction conditions employed. Amine groups up to 5 to 99% in thecollagen could be substituted. Radio-opaque albumin, collagen orantibodies can be useful in many other medical applications.

EXAMPLE 38

Radio-Opaque Implantable Collagen or Animal Tissue

Tissue Modification Using Iodinated Compound

a) Synthesis of N-Hydroxysuccinimide Ester of Triiodobenzoic Acid(TIBA-NHS)

1.2 g n-hydroxy succinimide and 1.1 g of triethyl amine are dissolved in100 ml benzene. The solution is cooled to 0° C. in ice bath. 1.2 gtriiodobenzoyl chloride is added dropwise to the cold alcohol solution.The mixture is then refluxed under nitrogen atmosphere for 3 h. Thesolution is filtered to remove triethylamine hydrochloride. The ester isthen isolated by removing the solvent. It is further by columnchromatography.

b) Chemical Bonding of Triiodobenzoic Acid Derivative to the Tissue

Modification Bovine Pericardium Tissue

Ten 1 cm by 1 cm bovine pericardium pieces, cut from a freshly obtainedbovine pericardial sac, are transferred to 50 ml conical flaskcontaining 10 ml phosphate buffered saline(PBS, (pH 7.2). 250 mgtriiodobenzoic acid succinimide ester, TIBA-NHS ester dissolved in 0.5ml dimethyl sulfoxide is added to the tube and the solution is vortexedfor 15 minutes. 0.1 g of TIBA-NHS in 0.1 ml DMSO is added to thefixation solution every 2 hours up to six hours. The modificationreaction is carried for 6 hours at ambient temperature (25° C.) and thenfor 12 hours at 4° C. with gentle shaking. The reaction is terminated bywashing the tissue with 20 ml PBS 3 times. Finally, the tissue is storedin 30 ml 38% isopropanol and 2% benzyl alcohol solution at 4° C. untilfurther use. The triiodobenzoic acid moieties incorporated in the tissuemakes the tissue radio-opaque when viewed using medical x-ray imagingtechniques.

In another approach, ten 1 cm by 1 cm bovine pericardium pieces, cutfrom a freshly obtained bovine pericardial sac, are transferred to 50 mlconical flask containing 10 ml MES buffer, (pH 6.5), 2 g3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid, 2 g Iopamidol, 2 g EDCand 1.5 g n-hydroxysuccinimide are added to the MES solution. Aftercomplete dissolution, the tube is transferred to refrigerator and thereaction is continued for 48 hours with occasional shaking. The tissueis removed from the tube and washed with 10 ml PBS 3 times to removeunreacted chemicals. The visibility of iodinated tissue is compared withunmodified tissue using standard medical x-ray equipment. The miffedtissue showed better visibility presumably due to chemically boundiodinated moieties.

EXAMPLE 39

Hydrogel Based Ultrasonic Contrast Agent and Methods for Making the Same

Part 1: Synthesis of Polyethylene Glycol Lactate Copolymer (PEG20KL5) 50g PEG molecular weight 20000 is dried at 120° C. under vacuum for 10hours. 10.0 g dry PEG molecular weight 20000, 2.2 g of dI-lactide and100 mg of stannous octoate are charged into 100 ml flame dried roundbottom flask. The flask is then connected to argon gas line and thenimmersed in oil bath maintained at 160° C. The polymerization reactionis carried out for 16 h at 160° C. The polymer is then dissolved in 100ml toluene and precipitated in 2000 ml cold hexane. The precipitatedpolymer is recovered by filtration and dried under vacuum for 1 day at60° C. It then immediately used in next step

Part 2: End-Capping of PEG20KL5 with Polymerizable or CrosslinkableGroup (PEG20KL5A)

30 g of PEG20KL5 is dissolved in 450 ml dry toluene. About 50 ml oftoluene is distilled out to remove traces of water from the reactionmixture. The solution is cooled to 65° C. To this warm solution, 0.6 gof triethyl amine and 0.5 g acryloyl chloride are added. The reactionmixture is then stirred for 30 minutes at 50-60° C. and filtered. Thereactive crosslinkable precursor is precipitated by adding the filtrateto 2000 ml cold hexane. The precipitated polymer is recovered byfiltration. It is then dried under vacuum for 12 h at 50° C.

Part 3: Polymerization of PEG20KL5 to Prepare Microspheres

5 g of PEG20KL5 is dissolved in 10 ml PBS. 300 mg lrgacure 652(2,2-dimethoxy-2-phenylacetophenone) is dissolved in 0.7 g n-vinylpyrrolidinone to prepare a initiator solution. 75 microliter ofinitiator solution is added to the PEG20KL5 solution and the solution ismixed. The mixture is then poured into 100 mineral oil (high viscositygrade) and stirred vigorously. While stirring, the droplets of PEG20KL5solution are exposed to long UV ultraviolet light (Black-Ray UV lamp,360 nm light, 10000 mW/cm2 intensity. The droplets are polymerized intohydrogel microsphere. The viscosity of mineral oil is reduced by adding20 ml hexane to the mixture and the mixture is filtered to removepolymerized hydrogel particles. The polymerized hydrogel particles arefurther washed with pure hexane to remove traces of oil from the surfaceof the particles.

Part 4: Storage of Hydrogel Particles Under Pressurized Carbon Dioxide.

2 g of the hydrogel particles prepared as described in part 3 are storedin thick wall glass vial and the vial is filled with carbon dioxide gas(pressure 0.1 psi to 20 psi. The carbon dioxide dissolves under pressurein the PBS solution inside the hydrogel.

Part 5: Use of Hydrogel Microspheres Stored Under Pressurized CarbonDioxide Atmosphere as Ultrasonic Contrast Agent

The hydrogel containing vial is depressurized just prior to be used asultrasonic contrast agent. The hydrogel microspheres are dispersed inthe 5 ml PBS solution and injected in the human or animal body. Thehydrogel particles are visible when viewed using high resolution medicalultrasonic imaging equipment. The carbon dioxide gas dissolved in freewater of hydrogel slowly diffuses out of hydrogel surface due to changein pressure. This results into contrast enhancement due to change indensity of the hydrogel.

Many types of hydrogel microspheres could be used. Biodegradablehydrogel microspheres made from albumin, polyethylene glycol derivativesare most preferred.

EXAMPLE 40

Radio-Opaque Natural Polymer Based Compositions

Preparation of Radio-Opaque Albumin Made Using Zero Length Catalyst

In a 50 ml polypropylene centrifuge tube, 1 g of bovine serum albuminand 2 ml commercially available Isovue-300 X-ray contrast agent solution(Iopamidol solution with 30% organically bound iodine) was added. Themixture was stored at 4° C. until albumin is completely dissolved in thesolution. To this solution, 0.6 g n-hydroxysuccinimide (NHS) and 1 g1-ethyl-3-(3-dimethylaminopropyl carbodiimide) hydrochloride (EDC) wereadded. The reaction was continued at 4° C. for 72 until the liquid istransformed in to gel. The crosslinked hydrogel was washed with 10 mlPBS buffer solution 2 times to remove unreacted EDC,n-hydroxysuccinimide and iodinated compound. A portion of the gel wassubjected to x-ray imaging was found to be visible in developed x-rayfilm.

EXAMPLE 41

Preparation of Radio-Opaque Chitosan

In a 50 ml round bottom flasks, 0.5 g of chitosan is dissolved 10 ml in0.1M acetic acid solution. To this solution, 3 g3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid, 2 g EDC and 1 g NHS areadded. The reaction is continued at ambient temperature for 6 h and thentransferred to refrigerator for 72 h. The solution is then poured in 500ml acetone to separate chitosan. The precipitated polymer is washed anddried under vacuum and imaged using medical x-ray equipment.

EXAMPLE 42

Preparation of Radio-Opaque Hyaluronic Acid

a) Modification using 3,5-bis(acetylamino):-2,4,6-triiodobenzoic acid(esterification with hydroxy groups in hyaluronic acid)

In a 500 ml conical flask, 2 g of sodium hyaluronate is dissolved in 100ml 20 mM MES buffer (pH 6.5). To this solution, 0.5 g NHS and 2 g3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid are added. After completedissolution, 2 g EDC is added. The reaction mixture is transferred torefrigerator (4° C.) for 48 h. The solution is then poured in 2 Lacetone with constant stirring to isolate modified hyaluronic acid. Theprecipitated polymer is separated by filtration and redissolved in 100ml water.

b) Modification of Hyaluronic Acid Using Lopamidol (Esterification ofAcid Group in Hyaluronic Acid)

In a 500 ml conical flask, 1 g sodium hyaluronate and 40 ml commerciallyavailable Isovue-300 X-ray contrast agent solution (lopamidol solutionwith 30% organically bound iodine) are added. After complete dissolutionof sodium hyaluronate, 0.6 g n-hydroxysuccinimide (NHS) and 1 g1-ethyl-3-(3-dimethylaminopropyl carbodiimide) hydrochloride (EDC) areadded. The reaction is continued at 4° C. for 48 until. The modifiedhyaluronic acid derivative is isolated by precipitating it in largeexcess of acetone and dried in vacuum oven at ambient temperature.

EXAMPLE 43

Preparation of Thermosensitive Radio-Opaque Solution

In a 50 ml polypropylene centrifuge tube, 3.5 g of Pluronic F127, 5 gcommercially available Isovue-300 X-ray contrast agent solution(lopamidol solution with 30% organically bound iodine) and 1.5 gdistilled water are added. The mixture is stored at 4° C. until Pluronicis completely dissolved in the solution. The solution is fluid at 4° C.The solution is warmed to 37° C. in a preheated water bath. The solutiontransforms in to viscous gel after 10 minutes of incubation. Uponcooling the gel to 4° C., it transforms into free flowing fluid again.The free flowing cold solution and the gel at 37° C. are visible whenviewed using x-ray imaging equipment such as fluoroscope.

EXAMPLE 44

Preparation of Non-Crosslinked and Water Soluble Iodinated AlbuminDerivative

1 g of albumin is dissolved in 10 ml 20 mM phosphate buffered saline pH7.5. To this solution, 1 g 3,5-bis(acetylamino)-2,4,6-triiodobenzoicacid n-hydroxysuccimide ester, dissolved in 0.5 ml dimethyl sulfoxide isadded (example 34). The reaction mixture is shaken for 10 minutes andthe reaction is continued for 12 hours at room temperature. The reactionmixture is then poured in to 500 ml cold ethanol to precipitateiodinated albumin. The precipitated albumin is filtered and dried invacuum at room temperature until constant weight. Alternatively, thereaction mixture may be lyophilized and then washed with 30 ml acetone 2times to remove unreacted iodinated compound. Modified albumin showsatleast 1% solubility in PBS solution.

EXAMPLE 45

Preparation of Radio-Opaque Polycarbonate Polyurethane

In a 250 ml conical flask containing Teflon™ coated magnetic stir bar,10 g polycarbonate polyurethane, (Carbothane™ PC-3575A, ThermedicsCorporation, MA, USA), 3 g iopamidol, and 90 g dimethyl acetamide (DMAC)are added. The mixture is stirred for 48 hours at room temperature untilthe polymer is completely dissolved in DMAC. The solution/suspension isused to coat medical devices to make them radio-opaque. Spry coating anddip coating methods may be used. Multiple coats may be applied toachieve a desired coating thickness. The coating thickness may rangefrom few 2 microns to 2000 microns. Alternatively, the polymer solutionis added to 2000 ml methanol with continuous stirring. The precipitatedpolymer is filtered and dried in vacuum oven at 60° C. until constantweight. The dried polymer is extruded into tubes using standardextrusion techniques. The extruded tube is clearly visible in medicalx-ray imaging equipment. Such tubes could be used for making medicaldevices such as catheters and balloons used in MIS procedures.

While the preferred embodiments of the invention have been illustratedand described, it will be clear that the invention is not limited tothese embodiments only. Numerous modifications, changes, variations,substitutions and equivalents will be apparent to those skilled in theart without departing from the spirit and scope of the invention asdescribed in the claims.

The invention claimed is:
 1. A biodegradable composition comprising:three biodegradable polymer branches linked together, each of thebiodegradable polymer branches having: a linked end linked to the linkedend of two other biodegradable polymer branches; a free end opposite ofthe linked end, the free end having an iodinated radio-opaque moiety;and a biodegradable polymer region having a biodegradable polymerbetween the linked end and the free end, the biodegradable polymerhaving a plurality of monomers with a biodegradable moiety.
 2. Thebiodegradable composition of claim 1, wherein the iodinated moietyradio-opaque is selected from the group consisting of iohexol,metrizamide, iopamidol, 3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid,meglumine diatrizoate, iopentol, iopromide, ioversol triidobenzoic acid,triiodophenol, erythrosine, rose bengal, 2,3,5-triidobenzoic acid and3,4,5-triiodophenol.
 3. The biodegradable composition of claim 2,wherein the biodegradable polymer of the biodegradable polymer region isone or more of: polyethylene glycol, polycaprolactone, polyhydroxyacids,polylactic acid, and polyglycolic acid.
 4. The biodegradable compositionof claim 1, wherein the composition is liquid at room temperature. 5.The biodegradable composition of claim 1, wherein the composition isblended with other degradable polymers.
 6. The biodegradable compositionof claim 1, wherein the iodinated organic moiety is from about 3 toabout 40 percent by weight of the composition.
 7. The biodegradablecomposition of claim 1, comprising a bioactive agent.
 8. Thebiodegradable composition of claim 1, comprising a bioactive agentlinked to at least one of the branches.
 9. A medical device comprisingthe biodegradable composition of claim
 1. 10. The biodegradablecomposition of claim 1, wherein the biodegradable polymer of thebiodegradable polymer region is polycaprolactone comprising a pluralityof caprolactone monomers.
 11. The biodegradable composition of claim 10,wherein a carbonyl of the caprolactone monomers is located adjacent tothe linked end and opposite of the free end.
 12. The biodegradablecomposition of claim 11, wherein the iodinated radio-opaque moiety isselected from the group consisting of iohexol, metrizamide, iopamidol,3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid, meglumine diatrizoate,iopentol, iopromide, ioversol triidobenzoic acid, triiodophenol,erythrosine, rose bengal, 2,3,5-triiodobenzoic acid and3,4,5-triiodophenol.
 13. The biodegradable composition of claim 1,wherein the biodegradable polymer of the biodegradable polymer region ispolyethylene glycol, polylactide or polycaprolactone and the iodinatedradio-opaque moiety is erythrosine or triiodobenzene.
 14. Thebiodegradable composition of claim 1, wherein the biodegradable polymerof the biodegradable polymer region is polyethylene glycol.
 15. Abiodegradable composition comprising: four biodegradable polymerbranches linked together, each of the biodegradable polymer brancheshaving: a linked end linked to the linked end of three otherbiodegradable polymer branches; a free end opposite of the linked end,the free end having an iodinated radio-opaque moiety; and abiodegradable polymer region having a biodegradable polymer between thelinked end and the free end, the biodegradable polymer having aplurality of monomers with a biodegradable moiety.
 16. The biodegradablecomposition of claim 15, wherein: the iodinated radio-opaque moiety isselected from the group consisting of iohexol, metrizamide, iopamidol,3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid, meglumine diatrizoate,iopentol, iopromide, ioversol triidobenzoic acid, triiodophenol,erythrosine, rose bengal, 2,3,5-triiodobenzoic acid and3,4,5-triiodophenol; and/or the biodegradable polymer of thebiodegradable polymer region is one or more of: polyethylene glycol,polycaprolactone, polyhydroxyacids, polylactic acid, or polyglycolicacid.
 17. A biodegradable composition comprising: eight biodegradablepolymer branches linked together, each of the biodegradable polymerbranches having: a linked end linked to the linked end of seven otherbiodegradable polymer branches; a free end opposite of the linked end,the free end having an iodinated radio-opaque moiety; and abiodegradable polymer region having a biodegradable polymer between thelinked end and the free end, the biodegradable polymer having aplurality of monomers with a biodegradable moiety.
 18. The biodegradablecomposition of claim 17, wherein: the iodinated radio-opaque moiety isselected from the group consisting of iohexol, metrizamide, iopamidol,3,5-bis(acetylamino)-2,4,6-triiodobenzoic acid, meglumine diatrizoate,iopentol, iopromide, ioversol triidobenzoic acid, triiodophenol,erythrosine, rose bengal, 2,3,5-triiodobenzoic acid and3,4,5-triiodophenol; and/or the biodegradable polymer of thebiodegradable polymer region is one or more of: polyethylene glycol,polycaprolactone, polyhydroxyacids, polylactic acid, or polyglycolicacid.
 19. A biodegradable composition comprising: eight biodegradablepolymer branches linked together, seven of the biodegradable polymerbranches having: a linked end linked to the linked end of seven otherbiodegradable polymer branches; a free end opposite of the linked end,the free end having an iodinated radio-opaque moiety; and abiodegradable polymer region having a biodegradable polymer between thelinked end and the free end, the biodegradable polymer having aplurality of monomers with a biodegradable moiety; and one of thebiodegradable polymer branches having: a linked end linked to the linkedend of seven other biodegradable polymer branches; a free end oppositeof the linked end, the free end lacking an iodinated radio-opaquemoiety; and a biodegradable polymer region having a biodegradablepolymer between the linked end and the free end, the biodegradablepolymer having a plurality of monomers with a biodegradable moiety. 20.The biodegradable composition of claim 19, wherein the one biodegradablepolymer branch lacking the iodinated radio opaque moiety on the free endincludes an antibody.